Pumeco: LOL, you are making this more complicated then it has to be, so my answer is NO an YES. LOL.

NO; I have no clue about how to set the Poser node U_Scale in Zbrush to do the same thing in Zbrush.

But YES; In Blender or Zbrush, you can subdevide the figure and sculpt the SubD version to add details.
Then, in both apps, you can "bake out", bump, or displacement or normal maps, to transfer your sculpt into maps.

Again, you"ll have a head and a body map. 2 maps to handle.

Using the trick above; Again merge both maps into a single wide map, and voila. . . one map to handle.

And if you did the merge of the material zones, far less work in Poser afterwards. 

Poser 1, 2, 3, 4, 5, 7, P8 and PPro2010, P9 and PP2012, P10 and PP2014 Game Dev
"Do not drive faster then your angel can fly"!