In that case, how about some HRE pro civ which isn't strictly unified? I'm sure someone made something like that, but I can't remember who it was. Also, do the Picts really count as Britons? I'm sure I read something about them being different, so it was more a Picts-Britons-Gaels split.
Back on topic, do you need any art done? I may be able to get something done.