The latest rumor for the next aircraft will be hang gliders dropped from hot air balloons.
With horse cavelry deployed from the gliders!
I'm for ANY new or revamped plane. Off the top:
Japanese twin heavy fighter
Hs129
Wirlwind
G.50 or Re.2005
Additonal versions of existing planes:
Stuka w/ 20mms
Ju88, the ground attack versions
Tse Tse
Apache and mk1 stangs
B-25 j
Many more I'm sure