OP's suggestion is not to prioritize GS below Silver, simply that CPU's ought not to be run until the gate. At that point, CPU's are run and GS presumably are at the top.
This does take care of the problems UA has created for itself when people in paid F with flexible tickets or willing to pay a change fee, can't change to a new flight because a Silver got the CPU. Same for a GS who can't change/SDC into F.
Logistically this is handled by the GA simply running the UG list and not mucking with it.