The hole that really needs to befilled is Biplanes, there were allotta WW2 biplanes and they played a very important role in ww2 from early war to midwar/early late war. they would be very usefull could outmanuver any other plane the let version I153 had 2x20mm cannons, retractable gear, carried more fuel than spitfire. And the CR42 was tied with the hurricane we have now, Hurricane had top speed of: 314MPH and C42:312MPH only a 2 mph differance!
And There was a very fast italian biplane dont know the name of it though.