I'm no "expert" by any means. But, I did grow-up on orchards in south-central Pa. and worked them for awhile. I've seen this done with a cutting and root hormon, with so, so results. And I've also seen it done, where a part of a branch is carefully de-barked, then wrapped with sphagnum moss and burlap. Keepin this moist it will start producing roots.(root hormon can also be used in this) Ok here's where memory gets a little fuzzy.(sorry) The time it takes to produce enough roots, to where you can cut the branch below the "new" root ball, is what I don't remember.
The only thing about doing this type of propagation is. It will take along time for it to mature and produce. All the trees that are planted today are "grafted" to different types root balls. So the the tree produces fruit at a younger age. BUT, they DO NOT produce enough roots to hold the tree up. That's why most modern orchards are planted on fence lines or each tree is staked-up.There's alot of science in how they figure the combinations. The orchard company I worked at, had an acre plot, that they did different studies with Penn State university backing.
How old is this tree you're talkin' bout? Has it in pruned on a yearly basis? It may just need fed.
good luck!!