So I accidentally became Holy Roman Emperor, which has turned certain latent succession issues into major problems, and I'm hoping y'all can help me figure this out.
So I started as Duchess of Holland. I became Duchess of a neighboring duchy, I forget the name. I formed the Kingdom of Frisia, and granted the second duchy to a merchant republic. So at this point, my titles are Queen of Frisia and Duchess of Holland, plus count of all but the merchant republic's province within Frisia. The Kingdom of Frisia uses feudal election, and my new heir is the rocking awesome Genius King Frans. King Frans gets elected Holy Roman Emperor when I'm not looking, because the electors apparently realize he's the Tom Hanks of monarchs, if Tom Hanks was a Dutch redhead with an awesome beard. My eldest son is a Dullard, but my third son is a Genius, and Genius Boy is obviously the one I want to inherit. Fortunately, Frisia is set to election, and there's only one other elector. My plan is to try to use the big stick of the Empire to build up Frisia, on the assumption that I am unlikely to hand the Empire down to my son, and Frisia will continue to be our family's power base. That's the background.
First problem: apparently, the Duchy of Holland uses primogeniture, even though the Kingdom of Frisia uses election, and I no longer have a button for the Duchy on the law screen, so I can't change it. This is also true of all my county level titles. So Genius Boy is set to inherit the title of King, but the Dullard is set to inherit all the actual land within the kingdom. Is there any way to change the laws to fix that? For this generation, I'm planning to get the Dullard killed in a very unfortunate military miscalculation, and send the guy in between off to the Church, but I don't want to have to keep repeating this every time I don't luck out on my main heir.
Second problem: my merchant republic, who are a major source of my budget. Do they transfer their vassalhood from the Kingdom to the Empire when I became Emperor? Basically, when I die and the next generation inherits, will the merchant republic still be their vassals, or are they now vassals of whoever the new emperor is? They are within the de jure borders of Frisia, if that makes a difference.
Third problem: if I conquer more land as Emperor, or revoke titles from vassals or whatever, is there any way to make sure it's passed down to the people I want it to be passed down to? I really want to get the Duchy of Flanders for Frisia, and maybe conquer some more of Pomerania (I already have one county up there). Would assigning it to my heir work?