Personally, I'd like to see a better cabinet mechanic, perhaps something similar to Hearts of Iron 3 only using randomly generated ministers. I'd like to see power (or rather whose stats the game uses for bonuses/penalties) being distributed between the monarch and his/her ministers based on the government type. So in a Despotic Monarchy, all power is coming straight from the King/Queen. In a Constituional Monarchy, all administration related stats are coming from the Prime Minister and the monarch only contributes charisma/prestige, or something like that.
The Personal Union is a mechanic that has always been terrible in EU3, IMO. I'd love to see it changed to involve more interaction between the senior and junior power. The senior partner should have the ability to make changes to the junior, depending on the government type of the two. If you throw around your weight too much, then the nobles/officials in the junior partner will start to want a separate King/Queen.
The Personal Union is a mechanic that has always been terrible in EU3, IMO. I'd love to see it changed to involve more interaction between the senior and junior power. The senior partner should have the ability to make changes to the junior, depending on the government type of the two. If you throw around your weight too much, then the nobles/officials in the junior partner will start to want a separate King/Queen.