Alright, so I set out into this game to prepare a nice European setting for EU4. Playing Pagan Wales, I conquered the isles, formed Britannia, and then expanded into France, Aquitaine, and Britany. Eventually, East Francia completely collapsed, which is why I annexed that as well and after several campaigns against Viking raiders also took Sweden and Norway.
Right now, the Druidic Briton Empire has reached a size that would be envied even by the Romans. Catholicism has been reduced to Moravia and Asturias, while the Byzantine Empire controls all of Italy except the South, which has fallen to a Merchant Republic.
It looks like a fun setting, but my problem is this: The year is 1180, and by 1444 I will likely have either conquered all of Europe or died of boredom. At the same time, however, I do not want to be overrun by the Mongols and Aztecs (running SI) later on, so splitting the Empire by manually editing out the Imperial title or releasing the non-de jure realms is also out of the question.
What I would like to ask of you is this: do you have any ideas on how to make the remainder of CK2 fun without steamrolling all of Europe while surviving the Mongols and Aztecs, and eventually having a nice Europe with several powers instead of just one to port into EU4? I'd appreciate any input.