
(X)
Levitate: Galvanize would have been better, but its biggest buff is Volt Tackle boosting its Atk anyway.

(Y)
Transistor: I think long term it's gonna be a really broken and problematic Pokémon. Transistor seems really good and
Levitate: Really classic pick and honestly it's a good one.
Technician: Shadow Sneak 60 BP woohoo. 151 Speed makes it not that impressive but let's start small shall we.
Tough Claws: Classic, but effective for clicking Brave Bird and Close Combat.

(Z)
Neuroforce: Doesn't fit lore wise indeed, and it seems strong, but not too strong? I expected Levitate, but I guess Neuroforce is fine.

(Z)
Mind's Eye: OK Mind's Eye is VERY strong on Lucario. Let's start big I guess? I don't really get it. Gonna be broken anyway, sure but idk.
Earth Eater: Excadrill makes it less good than it is, but it's a really fun Pokémon otherwise. It can play mind games whether it's mega or not (will you click Earthquake on that Heatran?)
Dark Aura: Knock Off and Dark Pulse boost. Hot take but I don't think the mega is gonna be worth it over base form, despite all the bulk. Maybe, and even certainly I'll be proven wrong.
Adaptability: Strong slow Pokémon. Not top tier but a really good mega overall.
Psychic Surge: I think it's gonna be a Mickey Mouse mega long term, at least Steels wall it? Let's see, boring but effective. I kinda liked Protean.
Ice Scales: Not boring but really effective. I like this one. One of the best options it had.
Regenerator: Sure, let's give the 150 Atk, 75/175/120 bulk Bug/Steel Pokémon with U-turn the ability Regenerator. The same people who wanted it will cry about Big Stall walling them. Come on, it's boring and honestly a really bad sight to have.
Soul-Heart: Fitting for a Pokémon who's gonna be Uber very soon.
Iron Fist: I think it's gonna be Uber anyway, but Iron Fist is fitting and interesting.
Contrary: Maybe it will save the latest victim from the SMAS (Slow Mixed Attacker Syndrom). Pepper thought it was Hoenn, and it doubled down when it mega evolved. Come on Scovillain. Do better.
Toxic Chain: OK I don't get it. Base form is insane, right. But you gave Toxic Chain to the Pokémon with Toxic Debris and Mortal Spin. How is it helping it, exactly? I don't see it, maybe there is a vision I don't have, but right now? I don't know. I kinda liked Merciless, Toxic Debris would have been fine, Corrosion, Levitate, Protean if you felt funky and wanted a "ayo I Tera'd" kind of ability. But Toxic Chain? On any other mega, sure. But on this one it's as good as Run Away.
Drizzle: Let's pray a moment for Drampa's soul, now being extremely outclassed. I don't really know what council went for, but if they don't know either, I don't blame them. Tatsugiri was the mega most people were uninspired for, I think.
Thermal Exchange: Stat wise, it's Kyurem-Black but it takes your mega slot and it has actual STABs. A lot of people seem to believe base form will remain OU, because no Loaded Dice, but come on. DD was already borderline in SV OU and NDOU, metagames with way more options. As for Thermal Exchange, it's the obvious yet still fitting ability.
Cold take but I prefer the mod without customs. Sure, I'm not opposed to custom abilities but:
- Keep in mind most gen 6 megas didn't have any kind of signature ability. Only Rayquaza and Kangaskhan. I mean, a lot of them did get Gen 6 abilities (-ate ones, Tough Claws, Strong Jaw, Mega Launcher...) but they were simple, and it brings me to my second point
- Most of the customs were... I'll say not to my liking. Brass Bond and Ange looked like something that could exist, but Ion's Battery was Levitate + x1.5 SpA. Contrarian was Simple + Contrarian. Protective Thorns was Iron Barbs + Bulletproof. Slapping 2 abilities together isn't good game design. And while I get why Malamar and Eelektross needed the boost to be usable at all, did Chesnaught need the buff? And Falinks was still bad. Oh, and Ange was extremely cancer to deal with. So sure, maybe I'll regret a bit the fact we have no customs, but I won't regret the ones we have (I will clarify, no shade thrown to anyone in particular).
That being said:
Bulletproof: Chesnaught but bigger. Should be enough to make it good, Iron Barbs was a bonus anyway.
Hadron Engine: People were claiming its death, seems like they were wrong. I can imagine it'll be as good as before, maybe slightly worse but it was due for a nerf anyway.
Dauntless Shield: It might help at least a bit, but it already has a good physical bulk. It doesn't benefit No Retreat sets at all, I guess now you can try being Zamazenta junior and go Iron Defense + Body Press? Seems like something that should be tried.
Regenerator: Boring but effective I guess.
Stamina: I advocated a lot for this one, and while Luchador's Pride was cool, I prefer Stamina. It might struggle a bit, but its niche is kinda cool.
Contrary: If only it got Speed instead of Special Defense. It tried to powercreep Ledian and almost failed. Comical failure with this one, and unless you go ape shit with Wonder Guard you cannot make it even remotely good. If it's still ass with Contrary I guess Prankster is another cool option?
Toxic Debris: Would have been cool pre DLC, but now you're gonna run Glimmora. Maybe in ZA ZU?