IMO, the most biggest things we could get, even if they aren't all truely 'additions':
1) update to ordnance selection system, more options. The 190F-8 has something like 1/4-1/3rd its historical options. It could also lug around 2x 250kg bombs (or maybe even 500kgers, nobody is 100% sure), 1000kg AP bomb, torpedo, 8x 50kg bombs, etc. The P-38 is missing some flexibility, as is the F4U IIRC.
3) Add Yak-7
2) Split the 190A-8 into early and late variants.
4) Add Ki-43
5) Add Wellington
6) Add the 109E-7, which can serve as a near perfect stand in for later 109E-4s, and high-altitude variants of the early E-4.
That should cover us to mid 2014 at least.