Spectral databases generally has a lot of data with similar chromaticity, including skin databases, although there are racial differences of course. In any case in terms of correction the default setting of DCamProf is to group together nearby patches and make an average correction for those. There's also a distance weighting algorithm enabled per default so it won't hurt matrix optimization either.
Anyway, in the tests I've done the CC24 skin patch gets lippmann skin sub 1 DE for 90th percentile, ie no meaningful improvement in accuracy can be had. The worst targets I've tested in terms of skin tone still gets within 1.5 DE for 90th percentile. It's hard to make any meaningful improvement on that. So no, a skin database will generally not make any meaningful improvements, not for caucasian skin.
"Excellent skin tones" in camera profiles that often comes up in the medium format forums is not so much about accuracy, but about a designed subjective look, and probably designed for foundation makeup rather than real skin. I'm quite sure that an accurate profile will not please the typical portrait photographer used to profiles with a designed look. I'm not a portrait photographer myself though so I can't contribute much when it comes to the subtleties of skin reproduction. DCamProf is not suitable for designing profiles with a look, but is rather for those of us that prefer designing our own look in the raw converter (or photoshop or whatever), with an as accurate as possible starting point.
In terms of accuracy, skin tones does not seem to be that big challenge for modern cameras, maybe there's been some consious design decision concerning camera color filters to make them good at skin tones, I don't know.