I pretty much always use different materials for the lips and nails.
generally when I get the skin I want I tend to look for lips and nails that i think work with it.

I did read in the vss discussion thread about changing rules and that which I presume can make the script bypass or ignore those areas. But have not even started looking at the rules side of it as yet.
Still catching up on that discussion thread though as it is huge and with so much information.
If you get around to doing the lipstick and other shaders I think it would be fantastic.
And honestly I dont know how you find the time you at present just to keep up with all the forums that you do.  Let alone keep improving things.