I'm going to do a Kalos only team, just to have fun with the new pokemon.
And since it's the 6th gen, I'll do a generational team as well, one pokemon from each generation to make up another team.
It might seem like overkill, but I did 2 teams in challenge mode black 2, and because of the new experience system I did fine actually. Was actually really fun because there's more of a challenge due to being naturally underleveled.
PS: I think this game will have the same experience system as gen 5, but I havent really heard any details about it. (Is this confirmed?) --- We had divine sense... To know what to say Mind is a razorblade