Coppiced black locust - advice needed

I'm at my place in Bulgaria and need advice on how to manage a black locust in the back yard right in front of an outbuilding and maybe 20 yards away from the back of the house. There's a huge ancient dead tree, and this one at the base of it seems to have sprouted from the roots.

It had been cut back in the past and the branches left to lie so I needed to first remove all the cut branches (now dry and just big enough to make useful firewood) from the tangle. The problem is now I am left with this thicket of new growth from the cut trunks, including some growing horizontal on the ground.  The thickest stem is no more than an inch.

I read that it's possible to coppice trees then select the best shoot and grow it out as a single. If that's possible with black locust, that's what I'd like. Ideally no more than three trunks, which seems to be how it naturally grows here.

Is this even possible with a black locust tree that's been messed around like this one has? If so, what can I do now to best achieve that? It's a late spring here. The wild plum is flowering but the black locusts all seem dormant still.

I want to keep the tree but I also don't want a black locust thicket in my back yard!

Edited to add - it's very strange! I'm almost certain the cut dead branches in the mess are black locust, spikes and all. And the cut diameters match the stumps. But the live growth from the stumps has no thorns at all and doesn't look like black locust! It's not wild plum and doesn't look like tree of heaven, either. So I don't know what I have here except that it coppices like crazy!