It's never too late. Step back, rewind, start over. A united Ireland under the British crown as before, with its proud capital in Dublin and its own sovereignty the same as Canada's or Australia's. I am a republican in the generic sense not a monarchist, but the petty nationalists have divided Ireland. That's exactly what they've done, not united - divided. I expect to be reviled by all sides for this idea, but this is the way to a united Ireland. It does not entail any loss of real sovereignty, laws or anything else, and it incorporates Northern Ireland into the Republic. If you claim to be for a united Ireland, you've got to start loving your unionist countrymen and give them what they want. Within a family, one sacrifices for the benefit of another. We should sacrifice our separation from Britain in order to regain our own unity on the island of Ireland. Does anyone doubt that countries such as Canada and Australia are independent? We had unity before, which was worth more than the present botched independence, but we squandered it. That is my opinion and I might be wrong, but there it is.
Update 22/2/2016: In the year of the anniversary of the 1916 rising, I am less inclined to believe that the above is a practical proposition.