Interesting article.
I too would agree that the bridge between unionism and a united Ireland is not actually as large as it may appear. One of the fundamental things which I realised over the years is that the vast majority of unionists have no problem with the Irish in general, just with the nationalists in the north. This was once made clear to me when a university friend commented that unionists would happily join a united Ireland tomorrow if the nationalists were not included. He stressed that their problem was one of trusting their neighbours not of trusting Irish people in the Republic. Fear of the Nationalists in the North sharing power with a government in the south and diminishing Unionism was what they were afraid of. Years of hatred between the communities of the north have raised these barriers that are so very hard to overcome.
Should they find peace among themselves then they are far more likely to wish to integrate with the south than the mainland. How to make peace with themselves when they don't trust each other enough to share power is the problem though.
paul.