We have some early war planes that made the cut such as the Brewster and I-16, would it be possible to add the P-26? Fixed gear and very slow, but was a decent plane in it's time. I've also wondered about the P-36. It saw decent time in the war with France and wasn't finally retired until the mid fifties. It did have weak arament but I think it could possibly join the Brewster and I-16 as early war planes in the game.
Just to try my luck some more, the P-35 is a decent plane, it could carry a decent bombload and had arament very similar to the Brewster.