[caldrail]

This is a list of planes that could have realistically seen production and done quite well in combat

Woah. The aeroplanes above were protoypes, not production ready military aircraft. Test beds and proof of concept in other words. The XP67 had some poor flying characteristics for instance and wasn't any better overall than existing types. The authorities weren't about to disrupt production schedules to make way for another type without good reason. The XP81 might have cut it, but it was also a large, heavy, complex aeroplane which I doubt had the same versatilaty as existing aircraft in the inventory, and in any case, the entire strategic rationale for its acceptance into service was circumvented by events.