I don't think that's the best solution.
Sometimes folks will skin multiple skins with little variation just to fill slots. There were about 4 nearly-identical P-47 skins put in for the same plane because ToD/CT might have a need for them, and because at the time the slots weren't full.
Now, we have no need for those 4 nearly-identical skins from similar units [edit: they may have since been rotated?], the CT/TOD is not going to use them, and they can be removed/benched/whatever to allow a bit more variety in the already-full P-47 skins.
Then there are times where a plane with all the skin slots filled has a lesser quality skin in place. Don't get me wrong I don't want any kind of ranking system, but things where basic alignment wasn't put into place, upper and lower stripes on wings don't match up, or gross inadequacies. If we had a P-51D skin like that and then there's Fencer's Big Beautiful Doll sitting in the queue, I would be perfectly okay with HTC saying "You know what, let's swap these, and damn the complaints"
(yes, even if they're swapping out one of MY skin!)
Totally subjective, granted, but I would think/hope HTC puts a bit of thought into the comparitive quality of the skins once the slot limit is reached.