How could a vote on the unification of Ireland play out?

How a referendum would be triggered and the options offered to voters are fraught with difficulty

Brexit has shown the dangers of failing to plan fully for the consequences of referendums, so what would happen if we were to get one about unifying Ireland?

There appears to be no chance of political leaders on both sides in Northern Ireland buying into the kind of pre-designed outcomes a referendum would require. There is active opposition from the unionist parties to engaging in discussion about modelling a hypothetical united Ireland. Why would we talk about unification? That would be like discussing our own suicide," said one leading unionist politician. On the other side, Sinn Fein will not be advancing arguments for a permanent place in the UK. So the chances of both sides agreeing the terms of a vote appear slim to none.