Yasha from Asura's Wrath, because Asura himself would be kind of difficult to implement, what with the lightning fast barrages of punches (especially if they decided to include Vajra).
I've always wanted to see a CV character in SC. I'm not sure how easy it'd be to implement any of the Metroidvania characters (I could see Soma, who could function similarly to ZWEI(WANT)), but any of the Belmonts could provide a fresh take on whip action, with some attacks using subweapons (and hell, Item crashes could be CEs).
I need to stop recognizing people by their signature. When life gives you lemons, shut up and eat your damn lemons.