I decided to imagine what the teams of gym leaders would look like if the creators of X/Y stopped treating the community like kindergarteners.
It's arguable that mega Pokemon could have appeared earlier, but I decided that the sixth gym was the best place for them to start appearing.
Valerie would obviously mega-evolve her Mawile, who is now her Ace. I replaced Mister Mime, because it didn't fit in with Valerie's "beauty" theme at all, and instead gave her two symbols – jewels(Carbink) and flowers(Floette). Also added Wigglytuff, because it symbolizes "cuteness." Clefairy is not found in Kalos.
Olympia doesn't have any Pokémon that can Mega Evolve to begin with. Slowbro doesn't fit her aesthetics, and Gardevoir is already taken by the champion, so that leaves Alakazam. I kept Meowstick from her original team to represent 6 gen, but changed form to female because it fits her more. The remaining places were taken by space related Pokemon, sun, moon and star.
Wulfric can mega-evolve his Abomasnow, but it seemed to me that Mega-Glalie would suit his aura much better. Avalugg stays on the team as he fits Wulfric's "big heavy menace" vibe and Cryogonal stays because I love him and he deserves it. The remaining places are occupied by a couple more heavy large ones: Mamoswine and Beartic.
So, should I continue with E4s?
by NikTheGrass