We have needed the P-39 for Eastern Front events for a very long time, and that should go a long way to getting better matchups, especially for 1943 era sets. It was always a choice of giving the VVS a P-40E or Yak-9T, or a LA-5FN and Yak-9U (a 1944 ride), so with the P-39D/Q that fills the gap nicely.
Just a quick comment, the LA-5FN is not a 1944 fighter. Its first action was Kursk in July of 1943. The Bf 109G-6 was one of its main opponents in the East, as was the Fw190A-5. The Yak-9U was definately a 1944 bird, although it entered service at the same time as the 109G-14 (not after).
In any case things are looking up, as the P-39 is one of the defining fighter types of the VVS in WW2.