I'd love to reslate Poliwrath tbh, given
-No Guard Dynamic Punch is boring and practically everywhere, and
-No Guard Hypnosis renders Hypno's niche inferior (Hypno is just bound to be worse than the better-typed better-statted Poliwrath if they have a similar role), which sucks given Hypno is supposed to be the master of sleep.
Totally agree on reslating Avalugg; Sturdy should not be on a single Mega pokemon.
Dedenne could use a reslate, but I'm biased because I really wanna give it a Technician to take advantage of Parabolic Charge and (an added) Draining Kiss; Electric/Fairy has unique dual-STAB on weird-gimmick low-BP draining moves.
My Furfrou's problem is that we went sorta nuts with Fur Coat on other megas. Perhaps a reslate just to make it an insane tank to keep up, something ridiculous like a 110 Defense with Fur Coat as well, otherwise it's bound to be outclassed unless we give it good recovery (which drastically improves regular Furfrou, flying in the face of this project's goal of improving via megas rather than blanket improving).
I say reslate Emolga, and I say that as the person whose Emolga won. Looking back, I feel like there are better answers than giving it a unique move like Parting Shot. Same goes for Jumpluff, Luvdisc (which should be reslated regardless), and Serperior. We got rid of Topsy-Turvy already, we should let Pangoro have its fun given our improvement of it. Again, the goal here is to improve megas, not base forms (Jumpluff in particular has a great Chlorophyll Parting Shot niche if the move is allowed in its base form, and standard Serperior can run an amazing screen set with Parting Shot and Light Clay).
We also have to reslate Unown. It's fucking criminal that we (and I use "we" lightly) gave Unown a move besides Hidden Power. If not a full reslate, then just fudge it so instead of move effects always occurring, that all of Unown's stats are boosted every turn a la Speed Boost (which is essentially what the winning submission does, without ruining Unown's gimmicky movepool).
I'd love to reslate Heliolisk, if only because Forecast would work so much better than made-up ability Doppler (Helio's Normal type could be switched like Castform's depending on the weather, which is just a better version of Doppler in terms of offensive Weather Ball output and defensive flexibility).
Kricketune and frankly all the starterbugs need to be revisited now that Mega Beedrill lets us make them viable.
Plusle and Minun are both not only unviable, but have ridiculous moves added. Freeze Dry Minun? Really?
Furret is underwhelming and has no flavor justification whatsoever for being Normal/Dragon.
For later:
Dragonite should be changed as well, given Storm Force is an absurd ability (Sand Force's boost to Rock, Steel, and Ground makes sense given the three's direct relation to sand; rain improving Electric and Flying makes sense thanks to Thunder and Hurricane, but Dragon? Makes no sense whatsoever, outside of wanting to make the ability fit with Dragonite).
Marowak should be reslated for a whole different reason: 105 Huge Power is already known to be bannably powerful (thanks Mega Mawile), and despite a worse defensive typing, Mega Marowak is even bulkier in terms of stats. Moreover it's got actual STAB on that Sucker Punch, STAB Pursuit to trap, STAB Earthquake for incredible power, and far better coverage than Mawile in the elemental punches and good Rock options to boot. Yes, this is a meta full of megas, but Mega Marowak is too strong even for that.