As for the CCAT so far, I personally think none of the nominations are sufficient for the team simply because I honestly have no idea why any of them are on there in the first place besides Rotom-W (cuz Lando + Rotom = love). The Slowbro seems absolutely superfluous because we already have Magnezone to trap Steels, so having Lure Slowbro feels weird, not to also mention people are going to assume Altaria is mega 100% simply because normal-Altaria is pure garbage in OU whereas normal-Slowbro is decent.
In my honest opinion, I find the lack of an answer to Mega-Sableye and stall in general the most pressing issue at the moment. Sableye pretty much screws over every single Pokemon on this team. Even Altaria gets murked by Will-O-Wisp. I mean, the Suicune set could help with dealing with Sableye 1v1, but realistically with stall, it's next to impossible, especially with Chansey on stall teams. Furthermore, this team has a pretty bad issue with Scizor and VoltTurn cores (Scizor/Rotom-W/Lando-T) in general. I really can't think of any good options off the top of my head, but these are things to definitely look out for.
You look like you know what you're talking about! Wow! I can't think of anything that would counter Sableye AND fit well on the team...If predicted correctly, Magnezone can switch in on Scizor. It's not gonna like Knock Off or Superpower though.