Body paints are a “second skin” humans have used for all of recorded history, and likely long before. In fact, earlier homo hominids, such as Neanderthal, may have also painted their bodies. (https://news.nationalgeographic.com/news/2012/06/120614-neanderthal-cave-paintings-spain-science-pike/)
I think it would be great in the game to allow body painting. One method would be to expose the body texture files so people could simply paint over them in their favorite image editing software. Texture files are easy enough to manipulate and would allow the player to individualize their culture a little. This could also be extended to ceramic textures for pottery.
Scarification, paint, piercings, and more could be readily drawn onto the textures (no mesh work or UV mapping needed).
P.S. This isn’t quite modding, nor is it clothing, which is why I made a new thread.