I think you're underestimating the Highland/Lowland divide in this period. The gameplay scenario you describe in which you find yourself wanting to use the accepted culture slot on something "better" is quite appropriate historically. If we wanted to translate the Highland Clearances into gameplay terms it's pretty close to Expel Minorities.
re: Wales. Wales was thoroughy "Anglicized" followiing the Ango-Norman conquests. It's a very different case than Ireland, which was very successful in resisting this process, or the Highlands, which this process at least somewhat ignored for various reasons.
re: Wales. Wales was thoroughy "Anglicized" followiing the Ango-Norman conquests. It's a very different case than Ireland, which was very successful in resisting this process, or the Highlands, which this process at least somewhat ignored for various reasons.