1. Improved culture system. A really stupid thing is that for example if I play as France, with the main culture being Cosmopolitan I can convert culture of the Basque province (can't remember the name) to Cosmopolitan instead of one of the Southern French.
2. Referring to the one above, provinces taking the states culture and religion (if autonomy is 0% for X years).
3. It's rather for a patch, but provinces should be made better for Poland. It was never divided into provinces like that, and we have the "Wizna" province which came out of the name of a city that's 1000 population today. I liked it way more in CK2. There should be just Polish region, like in CK2, instead we have "Wielkopolska" (Greater Poland) which takes all the north of Poland and Prussia (which is ridiculous) but in real life, just about two provinces. It's the same with "Malopolska" (Lesser Poland).
4. Redesigned technology system. Basing technologies on provinces would be great, especially if you play as someone like hordes and you conquer for example Russia, you could get their provinces with better technology and boost yourself. Also sharing it between allies would be a nice thing, also maybe stealing technologies.
5. Something better than the stupid rivalry... For example Poland and Hungary never had a war and they never had a war, but the system in the game puts them as rivals. Also, with some countries (France) you need to get proper rivals to have easy gameplay, and they are random when starting a new game.
6. Dynasty options. It's hilarious that you can marry unlimited people to one king.
7. Some nice things about Italy... right now it's difficult to create it, imagine the struggle of new players who are Italian or love Italy (I'm in the second group

)
8. More ways to spend money (additional, not required stuff, like canals).
9. Some crazy overpowered options like Sunset Invasion... Polan colonizing moon or something
