Sorry for the late reply! I'm having trouble following what you mean though. Basically, snapshot your gear at the start of the fight, turn on vanilla Inevitability of Rust rules, then restore the gear at the end of the fight but keep any new gadget?
You could totally do that -- and i invite anyone to mess with my scripts, though forgive my bad code (also check the dicey discord for modding help).
But I think at that point you're moving closer to Warrior than Inventor? The big draw of Inventor to me is continually changing how you play, and I don't know if between-floors is often enough. (Plus you could get screwed over by the "randomizer".)
I WOULD like to see a twist on Rust that's unencumbered by long-term planning, but I think you'd have trouble tweaking it to make sure you're always making interesting decisions.