What the *$* the point of digging up a design that's well over 65 years old, complex and costly to build, big, heavy, very inefficient by today's standards, noisy, and needs lots of room for take offs and landings. And that's before mentioning the servicing requirements and time. And 500 mph - at low level??
This was tried, as someone mentioned, with the P51, as a COIN aircraft which, although capable and successful for it's intended role, was too expensive, in relation to a new, modern design, and not as efficient in it's use of current materials. If an air force or army wanted such an aircraft as you envisage, I don't think they'd be looking at such an old design, just the same as they wouldn't regurgitate a 'modernised' King Tiger, just because it looks 'cool'!
Those air forces who still had P47's until the 1960's changed, not because the P47 was not a good aircraft, but because it was old, outdated and not as efficeient in it's required role in a modern world, as newer designs.
And by the way, the P51 wasn't a 'Cheap piece of junk', it was one of the most technologically advanced and efficeient aircraft of it's day, to which a lot of modern designs owe much. Or did the USAAF get something wrong??!!!
