I’ve been chatting with a friend about this topic. Together we know about as much Irish history as the dog around the corner, but we’re both quite intriged. As Mal said, many of the concepts related to the subject may not be commercially viable.
The good thing is about mod development is that it doesn’t have to be. Sure it helps if you want it to be a success, but not if you’re just trying to get some experience. This is something I may look further into. One idea would be to mod Age of Empires and have the four kingdoms of Ulster, Connacht, Munster and Leinster all kicking the life out of each other as well as making alliances and building up their armies. Anyway, I’ll think about it tomorrow on a fresh mind. :)