I voted for Toon Zelda, Dark Samus, and Other.
Though Toon Zelda would really just be a copy of Zelda, there are still differences that could be used for her. Toon Zelda was first introduced in the Wind Waker (really Four Swords, but that's beside the point) where she was Tetra at the beginning. With that, her down+B move could be a transformation into Tetra. Also, Toon Zelda would be less powerful and lighter than regular Zelda, obviously.
Dark Samus because Super Smash Bros. just needs more people from Metroid on the fighter roster. I can't really say too much about this though, since I still haven't tried to finish Metroid Prime 2 and 3.
Other. I say they should put in Airan Jo from Sin & Punishment in Super Smash Bros. Sin & Punishment is a great series, even only at two games, and has received representation in Super Smash Bros. Brawl. This representation was Saki Amamiya, who was an Assist Trophy. Because Saki was included in a Super Smash Bros. title, the possibility of Airan, and Saki, becoming a fighter is possible.