You're right in that the joints will more of less remain the same, but the UV map I don't think would hold up too well - mostly because (I believe) the material groups are tied to specific vert patterns.

I'm prolly explaining it all wrong (it's been awhile), but I can at least demonstrate it - set up a new material group in Poser (call it 'skinSomething')... notice that you have to mark polys on the figure or prop to do it. Now that's not the only way to rig a UV Map onto something, but I suspect that it's real popular in Poserdom.

Gross rotation? Not so sure - yes the body will bend and such, but how (and will the mesh tear?) I'm not so sure about.

You could always just lash the head onto something with a lower polycount already (like, say, Posette) - all you would have to do is build your own neck mesh and joint it up to lash the head and body together. Of course, none of the clothes would fit, but... :)

/P