Basically, a mod (or even an external tool, i dont mind) that generates a statue (1 block per pixel) of a skin file (either from a username or straight from a .png file) and generate a .nbt file to use it as a custom structure on datapacks.
Incredibly there isn't any easy way to make that barring from old mcedit filters (that doesnt work anymore) or shady bukkit plugins. Very niche thing, but would be greatly good for anybody interested.