really?  i find the benefits are far outweighed by the difficulties in practice.  i have literally never once used a zone for lips or nipples.i've only very rarely seen them used, and used effectively even less frequently.  and i've been around here for a pretty long time.  i really rarely see people use zones at all for clothing options, and i can't think of once when those were used with bump and displacement done by zone rather than UV. i have seen lots of 2nd skins, but again by UV not mat zone. and pretty much every single time i've adjusted anything on a figure, i've had to find a way to propagate it through several zones that take the same material.  no biggie, but no benefit either.

VSS is a really good option, but imho, it's pretty poor usability if someone has to learn to use a whole new tool just to do something pretty basic to 99.9 % of usage, where simply doing it differently would only affect 0.1% of usage.  and even then just affect, not prohibit.  it's really easy to make masks for regions like arms or legs (the most common use i've seen for materials by zone).  you can do it if you can use any image editor at all.  learning to use the grouping tool, in my experience, is not so easy.  not that i've spent more than a few hours messing around with it, but i've personally had less trouble with the cloth room and scripting materials, which is beyond many Poser users.  and learning to do the same thing in Blender, which many people find prohibitively difficult.