Well, I know there’s an .x importer script for Blender but I’m unsure how good it is. If it worked ok, I’m afraid the only way to do a merge of the two objects into one with the UVs from both would be to write a script to perform that operation.
It shouldn’t be too difficult if you’ve written Blender scripts before. It can probably be done in 30 lines or so. Maybe I’ll give it a crack and post it here.
EDIT:
Heh, guess 30 lines was an overstatement, here’s a script that does what you need:
from Blender import Object
s = Object.GetSelected()
one, two = s[0].getData(mesh=1), s[1].getData(mesh=1)
one.addUVLayer('UVTex2')
one.activeUVLayer = 'UVTex2'
for i, f in enumerate(one.faces):
f2 = two.faces[i]
f.uv = f2.uvJust select two objects, and it’ll copy the first selected object’s active UV layer into a new UV layer on the second called ‘UVTex2’. You might have to de-select and re-select the target object to see the change.