Surely the USAF should be using it's cash and time to train its pilots on it's own front-line aircraft - not a weird collection of odds & sodds??
Saying that's "50,000 hours gone" is silly - if hours flown is the only metric go out and buy a load of Cessna- 152's
Dissimilar training flown by guys who specialize in those types has to be a better answer than wasting a USAF pilot's time learning to fly a MiG-21 ...no?