A new gardener chopped down our 1 year old purple poui (Tabebuia impetiginosa) tree!! He clearly didn't have a clue about what he was doing...we asked him to trim the branches and cut the top as the tree had grown higher than our 1 story house. Instead he topped the tree at 5 feet from the ground and removed all the lower branches. Will it regrow or should we just finish chopping it down and remove it?
I don't know if it will grow again as it's not an evergreen. But perhaps you can save it if this only happened a few days ago.
I can also imagine trying to use a cleft graft on whole tree stumps, to make use of the root system or to save the tree. If you have to lose a mature (though perhaps not enormous) tree that you have an affection for, a cleft graft is one way to sort-of resurrect it.
You could take suitable twigs off a healthy part of the crown, cut the tree down, and then join the twigs to the stump via a cleft graft. You would then have literally replaced the tree with itself: a practical or sentimental alternative to replacing it.