I loved multiple nobles in the first iteration of the game. Having one Vampire in a big empire to mess things up while having a Conqueror start at a smaller group of duchies that crushed them while the Vampire kept the empire busy was amazing.
I can see the UI problem for sure, most of the time I ignore the voting anyway since it seems irrelevant to my goals. It's not like I can affect the outcome of the voting in any practical way if the nation I'm infiltrating is over a certain size.
Good to know about the agents. The number could change based on the default difficulty settings.