Yeah I wasn't meaning to imply that Mold Breaker shouldn't be banned, since I agree with you on that, was just using it as an example of how certain abilities check other abilities, and so I think a semi-minimal banlist would be better to start off to see how all the abilities play off of eachother. Glad to hear that not all the abilities you listed are going to be on the initial banlist as that was my main concern, I think we're on the same page here.
I think Regenerator should be looked out for but not threat #1. It has absurdly good synergy with Pressure, Multiscale, Fur Coat, Magic Guard and others and could make combating stall nearly impossible for any team that doesn't carry massive wallbreaking power. (Though that's pretty achievable here so, again, not sure how powerful it'd be in practice)
Charizard-Y sounds strong, and is a fantastic weather setter, but honestly doesn't even come close to the firepower (lol) of something like Greninja. On top of that, it lacks priority and has a 4x weakness to Accelerock. Not a big deal except for the fact that I can see Lycanroc-dusk getting used a lot in this meta as one of the only non-mega tough claws donors. It's very threatening with Solar Power, but that requires the use of some extremely niche mons, and most Adaptability mons don't really benefit from Drought outside of the Chlorophyll boost. Meanwhile, every Chlorophyll donor is having their own weaknesses exacerbated by the sun. I still think Sun could end up being a better weather option than rain, but that doesn't mean Zard-Y is busted. Honestly I feel sand could be the most threatening atm.
Agree that banned abilities should still be allowed on mons that already get them and just not spread, at least at first, there aren't too many issues that spring to mind immediately other than Shedinja who would obviously need to be banned.
Also, like the core, but it seems a little underwhelming given how powerful a lot of this meta's threats could be.
Here's a fun idea that would devastate offense but be pretty lackluster against stall
Won't do great against teams with unaware, but Beast Boost + Moxie + Simple gives Stakataka +4 Attack after it's first KO, which it should have no problem getting in a meta where Surge Surfer, Swift Swim, Chlorophyll and Sand Rush are sure to be everywhere. Pair it with Dhelmise for even more raw power, and maybe a water absorb/levitate/sturdy user to ensure it has an easier time setting up Trick Room. If it sets up successfully, it can OHKO pretty much every offensive mon in the game with ease, even Fur Coat Kartana dies to +4 Steelworker Gyro.
Contrary + Simple is also really good against non unaware teams, the most obvious abuser I can think of being Victini. Able to net +2 Speed, Defense and SpDef with V-Create, and +4 SpAtk with Overheat is nothing to scoff at. Pair that with Stored Power and you've got a pretty solid offensive threat on your hands. Stored Power also has the benefit of giving Victini a buff that isn't negated by Unaware.