I WOULD like to see fully custom skins, HOWEVER:
They should still follow historical paint schemes. So no goofy colors or out-of-place markings (IE, F4Us would need to be blue gray over light gray, tricolor, or overall gloss sea blue depending on what's appropriate for the different variants, with correct type of roundels).
Some of the custom jobs I've heard of just detract too much from immersion, but this would be a good way to regulate it, I think.