I'm having a bit of trouble visualising exactly what you're doing to set all this up, but I think I see what you're getting at. The hair doesn't need to come from any sort of subtle shape, though the mesh needs to suit the structure of the hairstyle. Right? How do you handle the edges? I assume you use a combination of transparency and putting the edge-polygons "under" the skin, so the hair appears to come out of the figure.