To use the standards you wish used, the 4th FG, 354th FG, 332nd FG, 52nd FG, 325th FG 339th and 31st FG all can be represented by one plane because they have "red trim"
Well, not to put too fine a point on it, but...
EXACTLY!There's no way you *can* get every important squad and every important unit, let alone minor ones along with that. There's no way to get them all, especially considering that the majority all looked the same. When you're talking a plane that's 95% bare metal anyways, on 90% of all the paint schemes ever used, and your red trim is 1% different from the next red trim, you literally have a plane that is 99% identical to ones we already have (with a different code on the side, and the angle on the red on the nose higher than the other plane), well... you've got the same skin.
If you like the red, take the red. We don't need 15 identical reds to choose from because then we have no other skins to choose from.
It's not a limited-slots issue, it's a ya-don't-need-to-nitpick issue.
This may seem calous, but just use the red skin we already have. It's so damn close to what you want.
When I pick a skin for any plane I'm flying I don't say "Oooh, I can't fly anything other than JG54, because I love that squadron" nor do I say "oh man I just can't fly that p51d with the red trim but is from the xxxth FG, I need to fly the one with red trim from the yyyth FG". I don't look at the units at all. I look at the skin. If I see it's got red on it, and I'm looking for red, I use it. Simple as that. I'm sure most folks operate that way, too, in regards to choosing skins.