They could make a fortune by adding more paid historical skins for planes, people willing to spend a couple bucks on a skin would be happy to have their plane muh spescial and the gameplay would feel cooler overall with more variety.
Look just at the Macchi 205 that had a ton of cool variants, even with german markings, and we are stuck with the base grey and that tremendously hideous anniversary skin.
See how cool it looks… they be sleeping I say, sleeping!