As per Ranika's advice if we added a Scottish or Irish faction it should be Scotland and there is no historical accuracy of a Gaelic Confederation, though it would be nice.....
Thats no reason why we shouldnt have the Irish in as a faction saying its ahistorical is rubbish because everything about the game is ahistorical the Irish and scotland wernt united in real life but in the game who's to say? The whole point of a game is that something different can happen every time.