personally, i'm going to try making my own maps for precisely these reasons.  everything i've read about texture making seems to advise mostly painting from scratch to avoid burned in artifacts, and i have seen photoreal results from this.  may be a fool's errand, but if i get it to work the way i want, i should have a fair amount of flexibility off of a few textures.

oh, and if you want the amount of red in texture, take the red component and divide it by the sum of all the three components.  if the texture has burned in SSS and is only skin, this will give you something of an SSS map.  i'd bet bagginsbill has a way to mask eyebrows and body hair.