We DID the work to upgrade our F-111s. It was called Pacer Strike for the F-111Fs and AMP for the EF-111s. Turned MX nightmare pieces of junk into very reliable jets - operating cost/hour just slightly higher than an F-15E.
The government could have kept all the EF-111s and a squadron of F-111Fs flying for the same cost as the 20 EA-6Bs - but the Navy was willing, and the USAF wasn’t.
One of the worst deals in the military - getting rid of the EF-111s and F-111Fs and taking 20 Prowlers instead.
The Aussies invented a way to NOT have to replace the wing pivot so often, that I havent seen anything about the USAF having. Apparently their way of fixing it, you dont have to mess with it again. They also have added a bunch of off the shelf electronic stuff that gives it new capabilities. There’s a fair amount of material out there about it, because their MoD is apparently as dumb as our Pentagon is when it comes to making upgrade vs new purchase decisions.
The best one I saw was upgrading engines to the same ones the F-22 uses. From what I saw it was a big nothing cost and engineering-wise, and made for a HUGE increase in capability.