Two young QBs only need one to groom.

U said it. Why have both? It is one season at a time, Starter, Quality back-up for 1-2 wins, a young for developing. 2 young ones for developing seems like playing for future only, what about the present?
I think Haener is seasoned enough that if he were asked to, he could be Brock Purdy-ish in the Shanahan/Kubiak offense. If the Head Coaching change leads to an Offensive Coordinator change, then I think Rattler offers a higher ceiling than Haener but maybe less reliable.

It's a good problem to have 2 rookie contract players worthy of getting a shot. If we can beef the O-Line a little bit and add a couple of receiving weapons, we're in good shape on offense