Although Krystal had a pretty negligible role in SFA (being trapped in a crystal... ugh... for 99% of the game) and multiplayer only capabilities in SFA... uh... Assault! (Its not my fault they have the same acronyms), I think she is a perfect character for SSBB. Everyone who is leaning towards a female fox clone... just no.
Her moveset is self-explanatory for anyone who played SFA. She wont use guns from assault - see comments on Snake not using guns - but her staff will give her everything she needs to be a mid-range speedster. She will be approximately half-way between Falco and Fox in terms of speed and height, but I think she should NOT have the shine. Her staff will afford her enough uniqueness and special abilities as is. I was also thinking that the ice move could be controlled vertically to a very slight degree (tilt up, down) freeze high damage opponents for split seconds and intercept projectile weapons. The earthshockwave would move from the inside out.
People are also forgetting that Krystal has psychic abilities, so if you want a confusion move like mewtwo's its reasonable. Her super could be to get all other players to fight each other and leave you alone.
Costumewise, the assault jumpsuit is more likely than the SFA bikini. Its just what she wears now. And its not like she threw the staff away once she got into an arwing, so its not out of place.
As far as placement goes, I would like Krystal to replace Falco in SSBB. Sure, Falco is top tier, but he is also boring. Wolf should be a Fox alt... theyre just too similar to each other.
For future games, the X button should change costumes and the Y button should change colours.
Fox's voice was fine in adventures. He isn't supposed to be freakin Barry White. I like both Assault and adventures fox - adventures being the young, confident and brash, assault being the older, cooler more experienced fox. Assault fox did look dumber than adventures fox.