Yeah, don't do that. You're asking for the game to shut off at best. They probably won't have the anticheat configured to outright ban you for that but, as a general rule: do not tamper with multiplayer anti-cheat protected games.

My recommendation would be to go to their discord and request the option.

EDIT: I will say this is overly cautious advice, I've never seen Crytek in general or any other developer ban people for using render alternating software that wasn't specifically designed to be a cheat.

You can use gamescope. There are keyboard shortcuts to modify sharpen filter.

Correct - FSR already applies CAS. I don’t think applying another CAS pass on top of that will work out too well.

True. I was assuming sharpening was disabled altogether, but if it's just set not strong enough, that's a different matter.