xxInfernoxx
[09] Warrior
If we're assuming it's Viola and Algol, and one of them gets in based on popularity, it would be Viola. https://soulcalibur.fandom.com/wiki/Soulcalibur_Series_Character_Popularity_PollSTAR to either Viola or Algol: Both have preexisting reusable models and don't have to be unclonified moveset-wise. However, Algol's not that popular, Viola on the other hand had Amy's face in SCV, so I have no idea how they'd solve that issue with Amy being confirmed...They could either re-conceptualize the whole character or even give Viola's orb to Algol, just to retain the moveset (which would be the cheapest way to do it, I guess). That one's a tough call, can't really say...I think that Yun-Seong as STAR is rather unlikely as that would mean that they'd have to develop one more completely new, unclonified moveset (but would have to let other people down who could't switch to a similar character like Yun fans could to Hwang).
IMO these would be the most cost-efficient solutions to the puzzle.
I think it would be pretty easy for them to re-conceptualize Viola into being a seperate character. They can just take her alternate costume, maybe alter it a bit if they want, and then change her height and face (Hey, if people can mod faces in SCV by hex editing, there's no reason PS can't do it.)