I think a new, improved range of skin textures would be a major boost.

Look at the Oxygen texture sets at rdna perhaps...? Not an extensive ethnic range I don't think there... yet...?? But on a production quality basis I mean.

I'm thinking of some good high end base textures, with proper bump / displacement / specular maps?

There is some scope in the HSV node... but different skin types differ by more than just color hue, don't they?

Merchant Resource packs covering a range of skin types, made to current quality standards, SSS and IDL friendly diffuse maps etc, would be a major boost I think?