There is no way the Island will settle for a hard border with the ROI and I think Unionist in most part know that a hard border returning to the Island would be the final nail on the head for Unionism.

The support for a United Ireland is sitting close to 50% and growing. I would wager the support for a hard border between Northern Ireland and ROI is significantly lower.

Either way putting a hard border up between Northern Ireland and ROI would be a disaster and would do nothing for the support for Britain on this Island. I was born and raised in notorious loyalist areas in Northern Ireland and the support is already dipping and conversations are happening now in these areas that could have got you put out of the area even 10 years ago.

I get the point you are making and I do think it is a valid counter but I don't feel it is a likely scenario. Then again 10 years ago I would have said a United Ireland in my lifetime wouldn't be likely and now I see it as almost certain so it wouldn't be the first time my judgement was off.