I'm not sure if it does this already because I haven't played with it too much, but it'd be cool if it deleted the skin from the server once the player leaves :D
Thanks for the review, this feature is now available on GitHub and will be here in 1.4.0 (in a few days)
Version: 1.2.0
Works wonderfully for 1.17
The biggest issue with other plugins that attempt to do the same thing as Skin Overlays is that they force you to go through an online skin database. This makes skin changes highly unreliable. This is the only plugin that actually allows you to maintain your own skins on the server files, and it works beautifully.