Fair enough. But the player choice is still there, only there are consequences to them. That's a concept that already exists in the game (witch outfit, sub collar, soulbinding, brint's armor, etc) only they're very easily avoidable, the only reason to engage w/ them is if you want their transformation side effects. Using magic wouldn't automatically make you corrupted, you'd just have to be careful. It would be like a cooldown you could ignore if you wanted to, but if you did that over and over again without letting it reset (by resting, going to some temple, etc) you'd gain 1 level of corruption. My main playthrough is with a mage who I want to keep pure, but there's no fun in that if it takes absolutely zero effort on my part to do so.
I understand it would be controversial, and I personally wouldn't trust the CoC2 team to make it a fun and engaging mechanic rather than a chore. If there is ever a true spiritual sucessor to CoC I'd like to see what could be done around the corruption content though. The element of activelly chosing to remain physically human & pure even though transformations & corruption gave you stat boosts, special perks and abilities was one of the highlights for me in the og game. Without that CoC2's setting is just bland medieval-ish fantasy sandbox where i'm playing the default route & have to go out of my way to find corruption content.