Don't get me wrong, I think for myself that Northern Ireland would be better off remaining within the UK than becoming part of the RoI, but it's a matter for the people of Northern Ireland.
What surprises me is that Sinn Fein seem to have no vision of what a united Ireland might look like other than absorb the 6 counties into the existing republic. East and West Germany didn't present it as a takeover of one nation by the other. Even China went down the 'one country two systems' road.
Northern Ireland has its own laws, judiciary, police, legal system, politics, legislature, education system, healthcare system (within the NHS) etc etc. The prospect of Gardai on the beat in Belfast, of laws being made in Dublin not Belfast, to me look like an occupation than a reunification. And that's speaking as someone who doesn't have skin in the game.
It seems to me an approach that said 'look, nothing very much will change, NI will retain all its own systems etc, will be essentially an independent part of a federal but united Ireland. But you'll be back in the EU.'' would be far more comforting to the protestant majority than 'Dublin is taking over.'
Has that approach even been suggested by Sinn Fein?