I don't know if you remember, but a while back we did some air-layering on a couple of different tree limbs. One of the ones we tried it with was a mulberry tree, and it worked great!
Abe opened up the ball of dirt around the de-barked part of the limb, and it was a very healthy root ball. He cut off the limb and put it into a pot. We are keeping the tree inside for now, by our south window, and it is doing fantastic. It has shown zero signs of stress and is even putting on some new growth.
So, not only did we do some needed pruning, we also got a fairly big and mature tree out of the process. It is definitely something that we plan to do again, and again, and again.