I don't think it's been mentioned as a possible feature in any of the patreon updates yet, but I think it'd be pretty nice to have. Chameleons and other color-changing characters are one obvious application. Another could be adding things like whip marks and red butt cheeks for BDSM scenes. Blushing, going pale, and other complexion changes. Applying or removing makeup. Tattooing is probably someone's fetish? Body painting maybe? Sex outside, getting dirty and grass stained?