The thing with the UI, given the economic realities as well as the division and discord it would, of course, sow, is would you really leave those people to The Brits?
Just looking at it from a pure ethical standpoint, well, that place is going loopy. Not only that but since the Blair government NI has pretty much been ignored by the various UK leaders. It's no wonder all the hope that came from the GFA is being thrown down the shitter, with the last of it remaining in the (quite a lot) of young-ish people who just want to get on with their lives. Then you look at Brexit and what that did for those young people, kids up to people my age who just wanted to travel and work in Europe, and see a bit of the world. Then you ask yourself again, "Would you really leave them to The Brits?"
Quick edit: From a personal standpoint I'd much, much prefer to see far more effort, especially from the UK side, on cross-border efforts and plans, but that doesn't seem to be happening from their side. They're not building up the north. They're creating a shithole, again, because they don't care. Just look at what Badenoch said about the north recently. They couldn't give a flying fuck.