Hmm: this core may be challenging to build differently from the known sample team with Mega Latias + Terrak (found @ the end
here). There's also another known team with this core
here (final member is Keld). They have similar structures because of the nature of the core. Weakness wise, the core's main issues are Mega Sciz and fairies (Mega Diancie, Mega Gardevoir, Clef). Tran quickly comes to mind as member #1 to help with these problems and provide SR. Assuming the team takes the Heatran route, things could end up going in a similar direction to the teams linked because Rotom-W / Landorus-T are nearly unmatched in terms of covering remaining issues like Exca, Azu, etc. Although something like Jira could be used over Tran to also provide SR and give us a better way to handle fairies, I still think it's likely the team will end up looking similar to the other builds. This is because Mega Latias + Terrak opens you up to some specific weaknesses and, generally speaking, only certain Pokemon patch them up better than everything else.
I am sure we could build a team that's different from the sample team, but then the question becomes: will our version be better than the original? Is there a way we can fix the original team's weakness to threats like Gar and fairies while maintaining a similar quality/some degree of variance? When someone sees this CCAT and compares the team to the original, would they be compelled to use ours instead? Despite the answer, I think it'd be better/more productive/more fun to spend our time building around a core that hasn't been explored as much. Could lead to more activity/participation from the community too. There are known/proven teams with Mega Latias + Terrak for people to refer to, and I don't know if it's worth trying to break the core's mold.
That's just my opinion though and I wanted to share the concerns. I know this core was voted for by the community in a really close one, but I think it's worth considering going with one of the lesser explored runner up cores instead of this one. Like
starry blanket said below, Band Terrak by itself is another fine idea.