As long as we get these Characters I think we'd be good:
Toon Zelda, who can change into Tetra.
Skyward Sword Link/Twilight Link. Maybe just a change costumes?
*Shulk is a must from Xenoblade no doubt
*Zael from the Last Story is also a must!
Aeron would be iffy, as that wasn't as popular as the other ones (Pandoras Tower)
Paper Mario would be kinda cool, not necessary.
Something of Animal Crossing would just have to come in!
*Rosalina is another must!
I don't really care for third party content. But if I'd have to choose, in my opinion:
Capcom: Chris/Jill from Resident Evil
Konami: Gabriel Belmont from CastleVania LoS
Sega: Sonic or maybe AiAi from Super Monkey Ball
Hudson: BomberMan!
Anyway its just all a thought.
Online would also need fixing! Haha.