I was busy testing Rhino WIP and this thread is one we wanted to see if we could get to work.
So I use ShrinkWrap to fix all the internal structure, then use the updated MeshBooleanUnion to union the frame around the outside.
Also, I guess I could Shrinkwrap > Quadremesh > SubD > NURBS and then Union in a Solid Frame. That results in a NURBS Solid.