What would be the harm of fully custom skins as long as they're kept appropriate, using the same or similar schemes as the historical ones (IE, mid-war USN/MC skins in "tricolor" scheme, single Star and Bar on the upper port/lower starboard wing surface, fuselage number forward of the fuselage national ensign, etc)?
HTC would still have the right to turn down a skin for whatever reason (anachronistic or otherwise inappropriate insignia/markings, inappropriate or derogatory noseart). This would just allow players to make the game a little more personal.