Personal preference, you keep Carr and you see if Rattler can beat him out in training camp. At the very least you hope it’s so close that you give it to player w/ higher ceiling
Given that Carr's not the future, I desperately would like to flush that contract, take the hit, and move on; if for no other reason, it seems his contract is an obstacle to building out the rest of the roster. But realistically, it just doesn't seem financially prudent (maybe even not feasible?!). Your scenario is probably the best we can do for THIS season. And I have no qualms whatsoever about Carr being the highest priced and probably best backup QB in the league if Rattler is the choice.