Actually, I can imagine late nineteenth-century ireland looking like the post-war southern US, with catholics in place of former slaves. There'd still be emigration to england and north america, but much more than OTL to urban ireland. The north would get a lot more catholic, while dublin would boom in population. As soon as you have a large population in a city willing to work for dirt wages, some british entrepreneur would see the oppotunity, and industrialisation will begin. Ireland by 1900 would be producing a few native industries, and actually acting like part of the UK's overall economy...