Sombra, yes the Yak-3 and Yak-9U look very similar. But the Yak-3 is much smaller, and a totally different airframe.
Performance wise, the Yak-9U and the Yak-3 are also similar, so for scenarios you could sub the -9U for the -3 and not hurt much.
I guess I would rather see Pyro put time into the Tu-2, Pe-2, P-39, P-63, Yak-9D, and some others before I would the Yak-3.
Even though it is one of my favorites.