BBP,
There aren't a lot of top end fighters left to be added at this point. Some mid range ones and some early war stuff, but unless you press for the very end of the war, and perhaps some just barely didn't make it fighters, there isn't anything that meets your criteria. Meteor Mk III and Spitfire F.21 could be added, but they are both perk planes for sure. F7F and F8F might be addable as they were in service, but missed combat, both are also perk planes. We're pretty tapped on on end of war German and Russian fighters. The end of the war for the Italian fighters, G.55 and Re.2005, would be nice, but they aren't going to be dethroning anything. End of the war Japanese fighters could bring in the J2M5 and Ki-100, but the Ki-84 is better. The Germans never got the Do335 in service and the Japanese never got the A7M or J7W in service.