Hey David, I know you are a bit of a AutoCAD guru. Do you mess around much with the 3D stuff?
We can generate a 3D textured mesh in a OJB or PLY file. Can that be imported into AutoCad and modify or add to it and make changes? I know that is a very broad question. I can send a sample file four you to play with if you want. We can talk on Monday on the phone if you are interested.