Well the only thing SoW needs is more Curtiss aircraft.
Seriously I'd like to see the air war in China before 1941 and the AVG.
The hottest things in the air would be Hawk 75s or A5Ms.
Lots of other little known aircraft that have never been done in a sim to my knowledge.
However, our politically correct world, and kowtowing to the People's Republic means it will never happen. Hell, we can't even have Nationalist Chinese markings in the game, officially.