A little mixed metaphor here -- MQM were for non-UA programs, UA used PQM
PQMs is a dead metric and not longer used by UA.
On rerouting on a UA ticket and *A carriers, your PQPs will not change. just like PQDs did not. These are based on what you paid. regardless if rebooked into a higher fare class.
If you get routed off of *A in the case of Irrops / INVOL, then you need to request
Original Routing Credit (ORC)
PQF may or may not change depending on the routing -- again if post lower than purchase routing, ask for ORC
Lifetime miles is another metric some are concerned about and if moved off of UA metal, it may post lower -- once again ORC to fix.