In order to produce a sweep with Z Celebrate (+1 all stats) NP Raichu-A, a few things need to happen before it can setup and clean without being RKed. Firstly, all potential Sucker Punch and other priority users have to be dispatched prior to setting up (e.g. Liepard, Absol, Shiftry, Skuntank, Golem, Kangaskhan, Dugtrio-A, Arbok, Dusknoir, Kecleon to list the most relevant ones). Then, there are a handful of Pokemon that resist Psychic and Electric coverage, like Cacturne, Shiftry, Togedemaru, Exeggutor(-K), Ferroseed, and even Raichu-A itself (Dugtrio-A too, technically, but Psychic overpowers that). Finally, bulky Ground- and Psychic-types can stop a Z Celebrate Raichu-A sweep if they're healthy, Piloswine and Mesprit being good examples of other potential barriers. So, I built with checking all of those Pokemon in mind.
For starters, I wanted an offensive pivot that would regularly bring in more passive, Psychic or Electric weak Pokemon like Weezing and defensive Qwilfish for Raichu-A to setup on. Primeape was an ideal partner for this - the threat of Close Combat consistently forces in Fighting resists like Qwilfish, Swanna and Weezing, which gives it the initiative to U-Turn into Raichu-A. Raichu-A naturally checks most of these Fighting resists with its dual STABs (the same logic applies to other less common Fighting resists like Roselia, Muk, Masquerain, Togetic, etc.). To add to this, bulky Psychics like Mesprit and Musharna are weakened by Primeape's U-Turn, making them less reliable for checking Raichu-A late-game after it has setup. Finally, Primeape does a decent job of checking Sucker Punch users, especially those listed above. Gunk Shot is an option over Earthquake for RKOing Lilligant from full, given that sets with HP Fire are problematic to most of the team. However, CC still does a minimum of 76% to boosted Lilligant and has a 18.8% chance to KO Lilligant after SR.
Next, I added Swanna for entry hazard control to keep Primeape healthy while it pivots into Raichu-A, and to address many of Raichu-A's checks. In particular, it resists Dugtrio-A's dual STABs and provides a switch-in for variants lacking Stone Edge, and checks some of the Grass- and Ground-types that Raichu-A has a hard time breaking from full HP like Piloswine, Golurk, Palossand, Torterra, etc. It forms a perfect entry hazard setting and removal core with Ferroseed due to the synergy they share - it resists Fire and Fighting moves for it, while in return, Ferroseed eats up Electric and Rock hits for Swanna. Ferroseed's Leech Seed and Stealth Rock are essential to weakening Raichu-A's checks, especially physically offensive Skuntank. Additionally, Ferroseed can pivot into Psychic on Primeape's behalf from attackers like Jynx and Mr. Mime in some instances, while also checking Archeops for the team with Gyro Ball when healthy. Lastly, it's important for pivoting into Kangaskhan's Fake Out for Raichu-A.
When you use Swanna, it's important to have a couple of checks to Lanturn. Between Ferroseed and Earthquake Gastrodon, all variants of Lanturn are covered well with Ferroseed handling HP Grass and Toxic variants, while Gastrodon can beat ones using HP Fire and hit it on its weaker Defense stat with EQ. Gastrodon is also nice glue here, and addresses a large portion of the physical meta, like physically offensive Carracosta, Kabutops, Skuntank, Lycanroc, Hitmonchan, Dugtrio-A, Archeops if healthy, Aggron, and other Pokemon like Magmortar lacking HP Grass. To finish out the team, I added Clefairy for a similar reason; Clefairy performs similarly with respect to the special side of the spectrum while supplying Knock Off support and a switch-in for Draco Meteors from the likes of powerful wallbreakers like Drampa and Exeggutor-A. Ferroseed + Clefairy + Gastrodon is extremely difficult to break, especially with Clefairy's Encore and Gastrodon's Toxic cutting into the opponent's setup opportunities. Clefairy has a chance to be 2HKOed by Drampa's Hyper Voice, albeit the roll to avoid the 2HKO is slightly in your favor, so you can pivot into mixed defensive Ferroseed. Likewise, if you don't know what it's going to lock into against Ferroseed, just Protect and pivot accordingly.
Overall, there are a few threats that are troublesome to the team: Haunter is very annoying, as LO variants break Clefairy and Gastrodon, while Choice Scarf lets it speed-tie with Primeape and outspeed Raichu-A before a Celebrate boost. Eelektross is also obnoxious to deal with, with Flamethrower hitting Ferroseed, Giga Drain beating Gastrodon, and AV walling Swanna. Psyshock is viable for hitting this much harder, as well as other SpDef tanks like Hitmonchan and Lanturn. However, using Psyshock over Psychic on Raichu-A means you won't hit Gurdurr, Piloswine, Torterra, Arbok, and Weezing as hard, which came into play occasionally during my tests.