Can’t say for certain. But I think I’m theory this should work.
Xgen uses mesh long names and ptex. As long as the mesh name doesn’t change. And the primitive (face) id’s and total stays the same you should be good.
I’d recommend doing a quick test with a sphere and see how the workflow handles it and what bugs pop up. Xgen can be unpredictable!!
As for merging the body in zbrush. There’s no way that’s going to work. It would break the maya long name and the ptex maps, as metering geos changes prim id. But you could recreate the hair as long as it’s not too complex. Just do all your attibute painting on the uvs and then export to ptex... i know you can do this is Mari, not sure about mudbox.
Let me know how it goes, I’m super curious.
