That’s fair. I think that this is probably beyond saving; it loses a lot of it’s flair without the ability to decide how many death throws to sacrifice (like chosing to cast at higher level).
I might try to salvage the exhaustion thing into a ring that allows you to extend the range or AOE of a spell by using exhaustion levels instead of charges or something.
FWIW most of what I read online seems to indicate that charisma most closely aligns with force-of-will. But it’s pretty murky, since like you said a lot of mind control magic is WIS save.