Move to Los Angeles. They have a few game companies looking for testers (no credentials required), EA most noticeably. Just don't expect to test anything outstanding (Barbie, sports, bull like that.)
As for the comment "Wii is 2x more powerful than NGC yada yada," the power has absolutely no relevance to how many characters can be in the game.
As for having a balanced character selection: Good luck. It took Namco 7 releases of a game before it was anywhere near balanced (the Tekken series,) and it's still not even perfect. Unless they hire videogame analysts and/or professional gamers in the community to assist them, I doubt they'll even know of half of the new advanced techniques that'll be discovered after the game is released. How many of the following techniques do you think were intentional: wavedashing, waveshining, superwavedashing, bomb jumping, desyncing, reverse blazer, blaster hopping, double jump cancel, etc, etc? One? Maybe two? Possibly none?
Unless they keep the exact same physics engine (which they're not,) don't count on an anywhere near balanced character list.
EDIT: Another thing about the max limit, stop saying "the game can probably store this much, blah, blah," because it's possible that the discs they're using could store up to hundreds of thousands of characters if they wanted it to. Nevermind that if they did have that many, they'd be nothing more than solitary two dimensional sprites and/or poor quality models.