Make Blemish - like the 'body hair' idea, make a way to easily add freckles, moles, birth marks, etc.
Crossbreed - Make it easy to pick and choose among ethnic types: Say I want 80% Germanic, 10% Han and 10% Swahili... I could just dial it in
Skin Color - make a special color chooser with the full spectrum of human skin tones, so I can just click on the one I want (of course, fantasy artists would want a full RGB spectrum)