This seems like an odd thing to find unrealistic in the grander scheme of the mod. There are probably thousand things that could be considered more unrealistic. Considering the point of divergence included England being conquered, there could have been an untold number of butterfly effects that could have affected Northern Ireland. It seems really strange to hold that Northern Ireland's demographics and political climate are just so set in stone in perpetuity compared to say, a new Boer War in South Africa or the Republicans and Democrats merging in America (to say nothing of something really out there like Atlantropa). This whole viewpoint feels kind of Teabooish, TBH.