Posted: 26/03/2016 at 18:11
I've seen a montana used this way DYL, but you need to improve the soil well, plant it a reasonable distance from the tree, and water well till established to give it a reasonable chance. Montanas don't need pruning so it's an easier choice than the ones which do. You can just tidy bits now and again to suit.
It's not something I care for because you still have the dead tree, but it would have a framework of branches covering it once it gets going