Hm, actually about that, a curious thing is that the morale might change according to the region. Of course, like any other form of recruitment, it's factored into the morale of the entire unit.
It would make sense, but I have never picked up enough volunteers to see any notable differences, so I could be wrong about this. However, it seems that the normal recruitment shows troops with starting morale linked to their home regions. It would make sense if the volunteers also came with the morale of their region.