mhhh well I would be glad to have RE characters! Leon, Chris, Ada, and Claire! man I would die and come from the death! oh yeah and Chcuk Norris too, but the game would be so awesome that only Chuck Norris would be able to play it, and it would be really easy to unlock because he would unlock himself XD
I would love to have Mega Man join the group. He'd have some great moves with the mega buster, and maybe give him some optional classic villain weaponry as special moves.
One thing I would love is to have an 8-bit option. Maybe not so much in terms of character selection like TP Link and WW Link, but possibly have 8-bit versions of characters as costume changes when you cycle through the colour options. It's not a new character as such, but I think it would be a hoot to have 8-bit Mario and Link fighting 3-D characters.