So I went through a couple of tiers and listed a few interesting ways a few mons might be able to be used in this meta. I of course haven't covered everything every mon can do in these two tiers but I hope this might help a little in terms of ideas for teambuilding. I also intend to go through the rest of the tiers in time. I also apologize if I tread over things others have already discussed.
OU
Special Attack Ferrothorn- Either take atk and spa and switch or, for more power, switch it’s defense and sp atk, but give it iron defense/leech seed/Giga drain/Flash Cannon. Remember that if you switch around it’s defense, it becomes weak to mach punch, and other strong fighting moves as well.
Physical Charizard Y- Switch up atk and spa (159 Atk). With access to a decent physical movepool, it’s possible for Charizard Y to hit harder and more accurately than before due to Flare Blitz. It also has access to aerial ace if you want to hit with a flying move. He also gets Earthquake.
Defensive Clefable- Switch up spa and def (95 Def)- Use unaware in order to make it more bulky. However, it can still be 2hko’d by a few mons in the meta, so beware.
Physical Gengar- Switch up atk and spa (130 Attack)- Physical Gengar is a lot of fun. He has access to drain punch for recovery, shadow punch, poison jab, fire punch, ice punch, sucker punch etc. He has a decent physical movepool and a not terrible speed base stat. However, he has a tendency to be outsped in this meta.
Physical Keldeo- By switching up its Attack and Special Attack (129 Attack), Keldeo becomes a physical wall breaker. He has access to close combat, swords dance, aqua tail, and other moves as well. Keldeo has already been proven to be an effective mon to have in a team.
Physical Latios/Latios-M- By switching up its attack and spA, you give it access to 130 Atk in non mega, and a blistering 160 atk in mega form. It has access to dragon dance to become even stronger, and it has access to recover, and it has a decent physical movepool to take advantage of. However, it does take up a coveted mega slot.
SpA M-Lopunny- Switching up its Attack and Special Attack gives it access to 136 special attack, in a decent speed tier. It has access to Hyper Voice, Focus Blast, and a host of other special moves. It has decent special coverage, but it’s fake out loses power due to the switcharoo (see what I did there) of its attack and special attack. However, it still has access to Scrappy, which makes it a good mon for ghost types, although the ghost type is not yet super common in this meta.
Speedy Pinsir Mega- By switching up M-Pinsir’s Defense and Speed, its speed base stat total becomes 120. This puts it into a better position to sweep after using swords dance. I tend to use facade with him so I can surprise my enemies with a very powerful move. It tends to wall break quite easily, and it has access to knock off to murder ghost and psychic types, as well as getting rid of eviolite from pesky walls. It also has access to close combat and quick attack, and thus Pinsir-Mega with it’s new speed stat of 120 becomes far more frightening to face. Also Remember that Pinsir-Mega has aerilate, thus making him somewhat terrifying.
Sp Defense M-Slowbro- Switch up SpA and Spd- By switching up its spA and sp def, you give slowbro a better ability to wall with its newfound 130 Sp Def stat. It also finds it easier to set up than before with calm mind, although you lose some power this way. It cannot be hit by a critical hit, so it can become a problem for your enemies rather quickly. It also has access to slack off, but remember how vulnerable Mega Slowbro can be to status if not properly prepared.
Speedy Tyranitar- Switch up speed and def- Slapping on a choice scarf to this speedy tyranitar gives it a amazing speed tier of 165. This enables it to hit hard and fast. However, I find it somewhat lacking in this meta, which is probably due to Chansey. We’ll see if it becomes more effective once Chansey is gone.
Faster M-Venusaur- Switching up its Speed and Attack gives Mega-Venu access to 100 speed, making it better able to sweep if that’s the route you wish to take. However, it might still be more effective as a wall.
Speedy Volcanion- Volcanion has always wanted a better speed tier, and in this meta it becomes possible to do a 110/120 Speed tier with choice specs. With access to Steam Eruption and Fire Blast as well as earth power and other coverage moves, volcanion becomes scary strong and fast in this meta. It’s my opinion it can become one of the best walbreakers in the entire meta, but don’t count on it breaking Chansey or Blissey, as unfortunately they are both still too bulky to be anything more than at most a 3hko.
Spa Weavile- When it’s Attack gets switched with it’s Special Attack, all of a sudden weavile becomes a dangerous special attacker. It has access to a decent special movepool, and even has access to calm mind or nasty plot if you’re brave or timely enough. However, it loses ice shard/fake out/ knock off power. This might reduce its role, I’m not quite sure.
Defensive Zapdos with Charge- This is a bit of a stretch, but it’s possible to switch Zapdos’ SpA with its defense and slap on the move Charge in order to make a more defensive Zapdos with a better ability to wall. Keep in mind that charge also makes electric moves stronger for a turn, so that might provide a advantage. However, charge is a lack-luster stat increaser, so I’m not convinced that Zapdos in this role would be effective.
UU
Defensive Roserade- Switch up speed and defense- Magical Leaf- Roserade has access to technician, which makes it’s moves stronger, but since this is a defensive set, it may not be as effective without its speed. It does have more survivability this way however. But it’s most likely still outclassed by Venusaur.
Defensive Snorlax- Defense and atk switch- With a switch of defense and attack, Snorlax’s defense becomes 110, which is equal to its sp def. With access to a great Health base stat total (160), Snorlax may prove to be an surprisingly effective wall. Give it curse and you might start seeing it laugh at fighting types. However, keep in mind it now has a very weak attack stat, so the switch might be more negative than you think. Think of this snorlax as more of a pseudo- Blissey. Without wish, heal bell, or really any of the cleric support Blissey can provide.
Special Attack Aerodactyl-M- Loses access to tough claws for the most part, but also loses its vulnerability to burn. You decide whether or not he’s worth it. Has a decent special movepool to take advantage of its newfound 135 SpA. It also has a good speed tier, but again, for the most part it loses access to it’s tough claws boost, so I’m not sure it’s worth it.
Special Attack, Speedy, or Specially Defensive Aggron Mega- Aggron can take it’s 230 defense stat and spread it to any of these stats above and surprise the crap out of people. But keep in mind that unless it’s speedy, it can be easily taken out by either a physical threat or a special threat. But I still believe Mega Aggron has a good place in this meta.
Speedy Blastoise-M- No drawbacks besides using a mega stone- Mega Blastoise now has a easier time sweeping due to a faster speed stat. With that it may become more effective at wall-breaking.
Pure Attack/Special Attack Cloyster- Defensive drawback, weaker to mach punch than before. But hits like a tank with 180 Atk/SpA- Attack is probably the best way to go here, as skill link is a nice ability.
Pure Attack/Special Attack Cobalion- Slight defensive drawback.
95 Speed Conkeldurr- Defensive drawback, Not enough speed to really take advantage.
90 Speed Crawdaunt- No drawback, but speed tier is still lacking, thus it’s defenses are still a weak point.
Special Attack/Attack Cresselia- Defensive drawback, probably better as a wall.
Special Attack Darmanitan- Extremely powerful Fire Blast without recoil, has a good special movepool, sheer force is very effective here.
Purely Defensive Donphan- Most likely outclassed by someone, probably forretress.
Attack Based Empoleon- Possibly not that effective, weak to burn, but decent typing.
Defensive Espeon- Surprisingly effective, has a good enough movepool and ability to pull off calm mind/morning sun role.
Defensive Florges- Decent Wall, but probably less frightening than 154 Special Attack Florges.
Specially Defensive Forretress- Good wall, has rapid spin/stealth rock- But not much in the way of recovery, unfortunately. Probably still more effective as just utility. But better at doing so with his special defense at 90.
Physical Gardevoir- Might possibly take someone by surprise, but weak to burn, and defense is still weak. Might be better as a physical wall.
Defensive Goodra- With its defense at 100, it’s possible that goodra might be able to tank better than before. Might have a better role in this metagame. Also consider switching up special defense and special attack/attack- Might be a very powerful attacker, but it’s speed tier is lacking in that capacity.
Speedy Gyarados- It’s speed stat can be switched with the special defense stat, making it’s speed 100. However, this is not a great speed stat in this meta, as a lot of pokes will be having their speed base stat higher than 100. So it might have a hard time fulfilling a speedy role. However, it does have access to dragon dance and moxie, which can turn it into a decent wincon.
Special Attack Haxorus- Honestly doesn’t have a lot to take advantage of here, as its special movepool is somewhat lacking. It has access to draco meteor, focus blast, dragon pulse, and of course, hidden power, but physical haxorus is superior due to dragon dance and a wider physical movepool.
105 Speed Hydreigon- Because the speed and attack stat are being switched here, Hydreigon doesn’t have a distinct disadvantage with the stat switch. Also, 105 speed is a decent speed tier, although it might still be slower than a lot of mons in this meta. However, with a decent spa of 125 and access to a decent special movepool, it might be able to find success as a special sweeper.
Speedy Lucario- It’s possible that in this meta Lucario can reach a decent speed tier of 110 or 115, depending on whether you want to go physical or special with it. Keep in mind that it still has frail defenses, but with a better speed tier and access to extremespeed as well as swords dance, it’s possible that Lucario can be more of a force to be reckoned with in this meta.
Special Machamp- Switching his Attack over to Special Attack- Special Machamp has proven to be very effective in teams I’ve used in this meta. It has access to No Guard, which makes Focus Blast always hit. He also has access to Vacuum Wave for priority, Fire Blast for coverage, and of course hidden power. Unfortunately, he does not have a huge amount of special coverage, and his speed is lacking. But, he is still a decent wall-breaker, and often surprises his enemy.
Speedy Metagross- Metagross can get access to 130 Speed by switching his defense around with his speed. This is obviously a very good speed tier, and in this meta, it serves metagross well. He has access to 135 atk, and as most of us are aware, he is often able to use that effectively. He also has access to Clear Body, which reduces the effectiveness of intimidate users against him to nil. However, remember that while Metagross has decent typing, by switching his defense around you are making him more frail than before. Thankfully, however, most people are still hesitant to hit Metagross with a physical move due to his steel typing, so there is still an advantage.
Special Attack Nidoking- (Switching up Attack with SpA) While 102 special attack is not amazing, with sheer force, all of a sudden Nidoking is a force to be reckoned with, even more so than before- Since he typically goes the special move route due to a better special movepool for sheer force, now with 102 special attack, Nidoking will hit a bit harder than before. I suggest going choice specs if you want to hit even harder. (NOTE: Nidoqueen can do the same thing, but with slightly less power and higher bulk. I recommend life orb due to having a higher bulk than Nidoking)
More Defensive Porygon2- Mr Porygon2 can have one of his defenses switched up with his spA, making him better able to utilize eviolite. I’m not quite sure which route would be better to go with Porygon2, either def or spdef- But in my opinion, this probably wouldn’t make much of a difference to shake him out of being UU in this meta. I’m sure however that he can still be utilized well.
Unaware Specially Defensive Quagsire- Quaggy can switch up his attack and sp def, making him better able to wall. However, he is probably still outclassed by Clefable in everything but type weaknesses. However, he does have access to recover, meaning he has easier recovery than unaware Clefable. He is, however, weak to status.
Physical Reuniclus- Surprisingly enough, Reuniclus has access to a decent physical movepool. He has access to drain punch, zen headbutt, and even superpower. It’s quite possible that Reuniclus might have a niche to fill as a physical attacker with 125 attack. As always, Reuniclus still has a weakness in his speed stat, but has decent bulk. However, he does not have access to bulk up like he does calm mind. He does have access to power-up punch though.
Physical Mega-Sceptile- Sceptile can get the attack he may or may not have always wanted in this meta, in being able to get access to 145 attack, which is a decent attack base stat in this meta. He has access to a decent physical movepool, as well as swords dance, so it is possible Sceptile can be a valuable mega to have in this meta.
Physical Sylveon- With access to curse and a possible 130/110 attack base stat and pixilate, it’s definitely possible for Sylveon to rise in this meta as a fearsome physical attacker. He has access to facade, return, double edge, wish for recovery, heal bell, and many other moves. It’s my opinion that Physical Sylveon can take advantage of its newfound attack stat and crush opponent’s dreams. (If you’re into dream-crushing)
Defensive Vaporeon- By switching up it’s special attack and defense, you may find that vaporeon has enough bulk to take on enemies easily. However, in a meta full of wallbreakers, you may find vaporeon outclassed. I’m not sure.