Here's a couple things I'd like to see:
F4U-1A - Best air-to-air combatant of the early-model Corsairs. Better visibility, armor, engine and stability (particularly on landing/takeoff) over the F4U-1, though not as heavy as the C and D.
PBY Catalina - She'd be a good, more versatile option to the Goon, and slightly less vulnerable since she carried guns in the nose and side blisters. The Cat could also be fit with bombs and torps, for some attack ability, or be used as a transport/supply plane. Ability to land on an airfield or water would make for an even more flexible plane.
P-39 - That 37mm cannon would be fun to play with.
B-29 - A bunch of guys were on the other night talking about wanting a good perk BUFF. Now THIS is a perk BUFF.
Nightfighters - Another conversation I saw in the game, adding true nightfighters with onboard DAR.
Player noseart/kill boards - Obviously would require require approval to be used, but it'd be pretty cool to decorate your plane with noseart and killboards.