>>36622497General reasoning behind each:
>Mega VaporeonAt first I wanted to do a "Storm Surge" ability and related Terrain, but scrapped it because they really don't need a Terrain. Water-Types are already pretty damn good and Vaporeon has already been one of the better ones for it's existence so the stat boosts are fine enough for me to not go OP.
>Mega JolteonAgain, Jolteon has always been one of the better ones. The stat boosts seem decent enough so I nixed giving it a more special ability, especially Electric Surge/Terrain (which as you may have started to suspect was my idea to give them all going in).
>Mega FlareonMade it a little faster and hit a little harder but compared to the previous two a Surge/Terrain seemed warranted. Nothing really to explain about the effects of it, I believe, as the effects seem pretty staightforward and reasonable.
>Mega EspeonNothing much to explain here, I don't think. It really is just a glass canon. Giving it a terrain seemed pointless with those stats. It's not like it's hard to set up otherwise if you want it.
>Mega UmbreonNot overly powerful in the Pokémon itself or the field effect it brings. I think the field effect works well enough though despite being pretty basic. Especially since it essentially prevents statusing Dark-Types entirely and Umbreon's defensive capabilities without boosts are already great.
>Mega Leafeon.Preventing status and stat loss is a fair enough trade off given it's already sweeper-ish tendencies and it's added stat boosts. Thus, again, no terrain seems reasonable.
>Mega GlaceonI think the logic behind this one is able to be seen if you know the metagame at all. Even with the boosts it's still an Ice-Type.
So... Don't mind me, just trying to fix Ice-Types in general a bit.
>Mega SylveonAgain, don't mind me... Just taking inspiration from Final Fantasy and Sailor Moon to not give it an ability that's not ridiculous but still useful.