Well, we'll see how it works out. I think that it should be a possibility for Spain, once you reunite the Peninsula, as the claim was made historically, but it was never widely recognized outside the peninsula. Indeed, it could be coded in such a way that it brought the man who used it in conflict with the HRE and Papacy, which happened historically. The title represented the leading Christian monarch in the Peninsula and was always tied with the city of Leon, and it originated in a period where the Iberian Christians were relatively isolated from the rest of Europe. It fell out of use in 1157, with the death of Alfonso VII, who divided his kingdom among his sons. But of course, things could have been different.
As to feudal "empires" like the Angevins, well it is trickier, because there was no formal imperial title. The fourth tier could be used in the case of a large dynasty with sprawling territory to denote the head of the dynasty, when there were strong tendencies for the leader of the senior line to help his brothers or cousins who ruled other lands in times of war. Finally, it could be created in an attempt to subsume several kingdoms together, which I understand was one of Ruwaard's points.