Aiddon
[10] Knight
Zasalamel could as well be a bonus character unlocked by completing some game mode or just appear in epilogue, forshadowing the sequel that will focus on SCIII-IV - just include him in the roster!
And Setsuka too, her style is complicated, but I'd like to try her once again.
Like I said, that's the only way to really reconcile it. However, with the roster only including 20 characters (at least at this point), I'm not getting my hopes up for anyone beyond SC1's original roster. Best to keep things simple and to the point instead of overstuffing things