Thoughts on the idea of their megas going:
>Mega Chesnaught - Grass/Steel>Mega Delphox - Fire/Fairy>Mega Greninja - Water/Fighting?
I think this would be the best way to do it. The secondary typings all work well with them and there would still be a type triangle for their secondary types, just going in the opposite direction.
Mega Delphox would also be the first Fire/Fairy type and Greninja changing types would help differentiate between his mega and Ash-Greninja (they could give him both forms like they did with Mewtwo and Charizard).
>>56472231 Is my favorite fan design for Mega Chesnaught.