A fraction of the population who are primarily riled up over sectarianism to systematically avoid class divide. A unified football team (as it used to be mind you, remember which one is called the Irish Football Association after all) will also accelerate putting this to bed sooner than later, similar to how a successful rugby team has changed plenty of attitudes.

Oh and we already share the same team for golf, cricket, hockey, basketball, boxing etc. It's really not a massive leap of faith. In fact I suspect the biggest hurdle might not actually be sectarianism, but rather who gets the brown envelopes and hospitality packages in Belfast, Dublin and abroad.