Quoted By:
>Pikachu
Absolutely essential. Been in smash forever, pokemon's mascot, some people have literally been maining Pikachu for years...you'd be an idiot to take Pikachu out.
>Pokemon Trainer
He's been used before, and he's actually a damned solid character. Some of squirtle's smashes are just terrifying, charizard is a beast, and ivysaur isn't bad at denying aerial attacks or abusing hanging from those vines on ledges. Loved doing that in sudden death. Not only that, but since he's basically Red, he's kind of like a secondary mascot for the Pokemon series in that he's the protag of the first games.
>Jigglypuff
Because there are people who actually use Jigglypuff well.
>Mewtwo/Lucario
Because they've been featured already and I can actually see either one having the warrior spirit to enter a smash tournament. Mewtwo especially. It only wants to test its ability in battle.
So that leaves two more possible characters. I say:
>one more pokemon trainer
An easy an obvious choice. This just leaves the question of who to pick. If we go with any of the other protags, I say it ought to be a girl, just for balance.
Lyra might work, and would make sense since 1. being from gen II would make her a good follow-up to a red-based character, and 2. she was on a DS system, which is relatively recent. May might be a good pick because of the Hoenn starters (Blaziken, anybody?), but I also thinks it makes sense to pick a more recent/relevant protag. So that leaves Dawn and Hilda. Personally, I think either one would work if done right, but I can't imagine how you'd work the Gen V starters into smash.
But why stick to protags? Why not a rival? Or a champion? Hell, Iris or Cynthia would be good picks.
And after that...
>Victini