Voting as concept is kind of weird when speaking about time period game suppose to mimick. King was the decision maker. Any war waged was in the name of the king. Every village,caste,town conquered in the name of the king. He decides if he keeps spoils of war for himself or grants them to his subjects. And here is where this game is missing a lot.
Every king had to watch that fragile balance between his supporters and oposition. To please everyone ment to project weakness. To favour only one house ment uproar among the rest of noble houses. And keeping this balance would be great game layer to be introduced. Inner strife between supporters,oposition,king.Noble house neglected by king, as example in case they would bare biggest costs in war conquering a city and not getting it as reward, would give this house right to wage war against king. But not to dethrone him. Just to get what is righteously theirs.
...and one more thing that always killed any of my previous playthrougs when I got to vassal and the king died. I was always voted as a new king. No oposition, no relations, not even member of ruling house...