Do you guys use vassals at all? I am playing as Scotland right now. I managed to be very aggressive early on and took over Britian. A little bit afterwards I marched into Flanders and took that as well. The French were not too happy that I took a region they had the right too but I managed to fight them off. I then fought a few back and forth battles with the French, eventually taking Paris, Rheims and Orleans, although not too easily with their fine cavalry. When I was threatened by the Pope I instead attacked the English in France and wiped them out. Spies opening the gates have been extremely helpful.
Eventually I got France down to one region but got a message to cease hostilities or face excommunication. Then when the mission was about to expire and I was about to attack a fair lass from France came to my door asking for a ceasefire. I said her brother who I had captured in battle and ransomed off would have to accept me as King if they wanted peace. He was not happy at all but begrudgingly accepted.
He has been a loyal vassal for around 6 turns or so, which surprises me because they basically have a full stack. It is mostly militia but has 4 generals. They pay me about 2500 a turn. They also do not seem to want the alliance to end, if I propose breaking it off in diplomacy it is Very Demanding, so I don't.
Since I was at total peace I decided to give the new Pope a lot of gold so he would forgive my sins and call a Crusade on the Moors. Unfortunately my Imperial allies beat me to Seville but I have taken Granada and will get Cordoba this turn. I can't have a meaningful peace with Muslims because of Jihads and them spreading Islam is a pain so I plan to destroy the Moors. Southern Spain and North Africa, however, will be awkward for me to hold since I have few generals and I don't want to adopt. Castile would be splitting my Empire. I am thinking of just taking everything from the Moors and giving the land to my vassal France, in return for their last region in France. They will manage the land and bring it back to Christ, while sending me tribute as well.
Does anyone else use vassals? Since I have thought outside the box I'm really interested in how this will turn out. Hopefully they do not become arrogant like Frenchmen often are and bite the hand of their King!
One note is that it seems if a vassal ends his turn with over 10000 gold, all the money goes to his liege lord. The French have been stuck at 10,000 for awhile now. I wonder how this affects construction and if I could send gifts to help them build Cathedrals.
Since this is a Historical Improvement mod, I think it would be a good idea for the game to encourage vassals and discourage the player from directly running huge Empires.