Scotland or Wales. Scotland seems best to me, unless you have a crazy Wales, it can happen, not often but it does. For Ireland, my best way is to take the lower 7 counties, create kingdom, destroy those 3 duchies if created, and then lord mayor up the top 6, and create the 2 northen duchies. Duke of Galloway and Albany are who you want on your side from Scotland imho, The Duke of Galloway will almost always at some point become King, if he is your family, England will not be able to mess with you. Ireland can become a powerhouse, I was able to have the #5 army with just those bottom 7 and the top 6 as vassals. The AI does not upgrade as good as the human does. Plus by staying small, you will not have faction or succession issues.