For Mario characters, Luigi should be further diversified from Mario by including the Poltergeist 3000. New characters should include one of either Bowser Jr., Toad, or Waluigi.
For Donkey Kong characters, K. Rool should be included.
For Zelda, Ganondorf needs his own moveset. Give him his damn sword. There is also no reason why Toon Link should be a clone of Link. There is so much to work with in WW, PH, MC, ST, FS, and FSA that it's just annoying that the time isn't available to make him unique. If any new characters are added, it should be Tingle.
For Pokemon, bring back Mewtwo. Change Lucario's moveset if necessary or replace him with Zoroark or a new Pokemon Rival (Blue/Green) with three 2nd gen starters. Mewtwo needs to return though.
For Star Fox, diversify Fox, Falco and Wolf more especially with Final Smashes. Also add Krystal.
For Fire Emblem add one of either Sigurd, Roy, or Eliwood.
For F-Zero either add Samurai Goroh, or if time-crunched add Black Shadow and give him Gonondorf's old moveset.
Add nothing new to Kirby, Mother, Wario, Yoshi, Pikmin, Kid Icarus, Ice Climber, Game & Watch, or ROB. Maybe change Lucas to give him some of the attacks he actually used in his game instead of those of his partners.
For new franchises to the series add Little Mac from Punch Out, Isaac from Golden Sun, Tom Nook from Animal Crossing, Ray Mk. III from Custom Robo and maybe Starfy.
For 3rd party characters, in addition to Snake and Sonic, add Mega Man from Capcom. If Maga Man is unavailable, get Ryu from Street Fighter. If Capcom is being skittish, Pac-Man from Namco Bandai, Black Mage or Sora from Square Enix or Ryu Hayabusa from Tecmo Koei are good. There should be no more than three 3rd party characters though and for the love of Miyamoto don't waste a space on Geno unless you're gonna give me a Geno game.
