Hmmm.... let's see.
1. More nose choices would be cool. Even some messed up ones, like broken noses, bloody noses. Hell, actual bleeding noses?? Not my cup of tea, but just throwing it out there. Whatever trips your trigger!
2. It would be cool to see some 4 color RGB dynamic hairs that "amp up" the details just a bit and allow for some really cool subtle highlighting (or wacky over the top madness) Somewhere in between most of what we have now, and the full blown real hair static mods.
3. I've always felt the eye shadow could have more "adjustability" on the alpha to have it show up like really super heavy. It could be there's something there I'm missing. If so, let me know.
4. Lingerie, lingerie, lingerie. I realize in profile your dealing with a "limited" area as well as difficulty in creating really fine detail. I guess specifically, I'd like to see bras, panties, garter belts that provide more RGB options to change colors on very specific individual elements. They would be 'intricate", but would be "pretty neat" to see a really good one. I RARELY use tongue piercing, nipple, or belly piercing so those sliders could be used to really provide some adjustability. Examples: a separate underwire (or trim around the breast area that is independent of the stra p or main fill color.
5. Up and down adjustment arrows with a number display in place of sliders so you can see exactly what values you have for breasts, body, etc. without having to generate and export char codes and then go look.
That's all I can think of for now.