"I have found that if I export as a .dxf, .vrml, or .obj (with the associated .mtl file) that the mesh in Rhino is untextured" Assuming you solve the grouping problem, can't you just export the maps from Poser and make Rhino "like" them?

There "was" a script to export .mdd out of poser and all associated maps, but I the link in the first post below is dead..

https://www.renderosity.com/mod/forumpro/?thread_id=2743741