2x MK103, 4x MG151/20, 2x MG17 (or possibly MG131). The 410 is definitely on my wishlist.
IMO we don't need the P-40N much. Sure, "it would be nice" but it was behind the curve of what was already in the war and fighting when introduced. Folks would say "But I love the P40 we have now, I'd like a better one" -- only the P-40N, should we ever get it, would have a much more realistic flight model than the first-generation P-40B and E models we have in-game. If they ever get updated to current (third-generation), they would most likely lose a bit of their effectiveness, as they will fly much more like 1939 and 1941 aircraft they are.
I've no doubt we'll get the Airacobra some day, but all we can guess is "2 weeks."
I'd rather see the G.55 (hey, I can wish!), the ki43, the ki44, the g3m, the g4m, the he111, the ju-188, and the ju88a-1.
But, we'll eventually get the P-39, don't worry.
