I think that the only characters that should be removed are ROB and Toon Link. I just believe that there are better characters out there that deserve a place on the roster other than ROB. As for Toon Link I do not see him being anything but a mirror to link in the next game and The Legend of Zelda series has better characters to offer then just mirrors. The other characters that are considered mirrors should be drastically changed to fix that, the following being these characters: Gannondorf (include his sword into his moveset and get way away from him being a Captain Falcon clone), Flaco (I like the direction that Super Smash Brothers Brawl took in trying to get away from him being just like Fox by making him throw his shield), Wolf (once again I like that they changed his moveset just a little bit by making his side B attack and an angle, but I would love to see him and Falco both get seperate smash attacks from Fox), and Lucas (he is already a little unique but a little more could not hurt.)
Pokemon Trainer was made to be just like Red the most memorable character from the Pokemon games, and I think dropping him would be a huge mistake. I think the problem can just be solved by adding either a Rival Trainer with pokemon from Johto, Hoenn, and Sinnoh or a Female Trainer with just Black and White generation pokemon.
The Lucario and Mewtwo situation is more of a difficult fix. Mewtwo was supposed to be in Brawl but was not inserted due to timing. I personally did not like Mewtwo's moveset and feel that if it is changed people will not be mad that he is back. Lucario sees a lot of play in tournaments and is overall a good character and I would like him to return but he is less likely I feel to return then Mewtwo. Then of course Zoroark is the new popular represenative of Pokemon so he will probably be inserted into the game. The only way to not overload on Pokemon characters while keeping the fans happy is most likely to bench Mewtwo again or Lucario this time with Zoroark taking the others spot respectively on the roster.
As for the third party characters I foresee Sonic comming back with maybe even another character from his games either Tails or Knuckles (not Shadow because I feel he will be another mirror even though he could have an original moveset I still feel like Nintendo would take he mirror route) but I do not see Snake making another appearance. Instead a good person to add in his place would be the blue bomber himself, Megaman, who would be a great addition or even Pacman since Namco is helping with the development. Please God let them add Banjo and Kazooie to the mix too.
I also see the Mario series adding two characters (Bowser Jr., Toad, Paper Mario, or Waluigi being the most likely), two new Zelda characters with Toon Link being dropped (Vaati and Midna riding Wolf Link would be my choices), one Metriod character (Ridley if they resize him, maybe Dark Samus with a unique moveset if they don't), one Donkey Kong character (King K. Rool), One Fire Emblem, Star Fox, or Kirby character (Lynn or Black Knight for Fire Emblem, Krystal for Star Fox, and Knuckle Joe for Kirby), and a F-Zero character (Samurai Goroh).
Lastly, newcomers I do not have that much of a grasp on, however. Isaac from Golden Sun, Little Mac, and a Mii character are the only ones I am sure will be in it. Ray Mk. II would be nice as would an Animal Crossing character (not sure who) but like I said I don't really know about this subject.
