Krystal needs to be in this game for three reasons:
1) Female character - We don't have enough, we need more.
2) Moveset would be original and creative - She would simply use her staff from Adventures. Enough said. Swing it aorund for A attacks, use its magic for B attacks. Not much else would be needed besides just a smudge of creativity.
3) Star Fox needs more characters, less clones - We got one new SF character in Melee, and he was a clone. Whoopie. I'd like original characters please, thanks.
And my fourth, personal, reason: She's a fox