I also have to say that the Alco PA was a classic. Even though it had a crummy prime mover it was one of the best looking locomotives ever built.
Has UP fixed up their trucks so three traction motors instead of two are used in each truck? That way UP won’t have to deal with the center axle being idled.
Maybe instead of a 645, they could use a similar 567 found in the SD35’s since the 567’s are more reliable than the 645. But you have to wonder that the flaw of a shortage of 567 parts would come into play.