What about the 1 million or so unionists in Northern Ireland? Who by their very definition want to keep the unionification with the crown? How can they be convinced to join a republic? Surely, they would have to re-define themselves as Irish protestants instead of british loyalists/unionists? Can you see this ever happening?
I remember being intrigued by what the unionist politician david Ervine once said about his idea of Loyalists/Unionists having to reassess themselves oncelebrating their "Britishness" rather than simply being anti-Irish. IT suggests that some unionists might see the inevitable and realise they need to redefine themselves. I suppose if they became an "ethnic moniroity" in the republic then they could milk EU for some money ;D
I often wonder if the idea of a borderless Europe will eventually lead to the idea of north/south borders in Ireland being an anachronism (if they aren't already).