I personally wouldn't cut anyone, even if there are a few I don't care about I wouldn't like to disappoint anyone, plus I'm not against any of the characters anyway.
If I had to remove a character, maybe Bayonetta, or just the Plant to be fair to them and other characters' fans. Though I'd actually like to keep the Plant, but it is the one you'd cut to be fair.
I'd actually just try to stuff more characters in without removing existing ones. We can have Steve and B-K together (yay), Creeper, Toad, Geno, Ninten, Porky, Gengar, Gardevoir, Tepig or Oshawott or whatever Gen 5 'mon, Slime, Black Mage, Goomba, Chorus Kids, Skull Kid, Sans & Papyrus...