It has two empireses: Russia and the Commonwealth.
In these countries culturess belonging to any cultural group (Slavic) wouldes be acceptables.
I'm sorry but this is nonsense. Historically Polish-Lithuanian Commonwealth had big problems with accepting one of those 'Slavic' cultures, let alone all of them. Those countries never constituted a center of all Slavic cultures the way China grouped all Chinese cultures.
By playing one of these countries one could create the Slavic Empire - gaining lands belonging to Slavic cultural groups.
It's not a real/historical concept, but a fantasy concept, therefore it shall not be added to EU4. But if you wish, you can make a mod with all the changes you want.
New provinces and new cultures will be added.
Eg.
Slovenian culture
Lusatian culture
Moravian culture
Podlasian culture
The main problem I see with that, is that all of those would only have one or two provinces on whole map, which doesn't really affect gameplay and they don't differ that much from what already is there (Podlasian? really?). Though I'd indeed like to trade Saxon culture for Lusatian in those two provinces applicable....
Pomeranian and Slovakian cultures were added to the group of West Slavic cultures.
Problem is that Pomerania and Mecklenburg (the ones currently having Pomeranian culture) were already germanized by 1444, but I would support Słupsk, Gdańsk, Tuchola having a West Slavic (Kashubian?) culture instead of Germanic ones. Slovakian should be moved to Western Slavic I agree.
Countries belonging to the South Slavic group could form Yugoslavia - to defend themselves against the expansion of the Ottomans.
Considering that the game even has Romania formable it's actually not too bad, but I'd make it late game easter egg or something. But it's not something very needed.
Added to the Commonwealth a special system of government - the Sejm.
A new elector will be elected in it after the death of the last member of the ruling dynasty. The term of power would last until the death of the ruler or his overthrow. The rulers who had had a royal dynasty with their former dynasty left the candidates for the king's election. There would also be special edicts on the rights of the nobility. When they get there then the ruler has more support when it goes back and leads the war of the gentry proclaims rebellion.
Commonwealth in EU4 already has its own kind of government - Elective Monarchy, but it could indeed use some improvements as it doesn't quite have mechanics one would expect.
You could also create a patch or DLC that would extend the game time (the beginning of 1409 - Polish-Teutonic War).
Eh, just no. The last 20 patches (plus the upcoming 21st) all aimed to improve game balance and experience in the 1444 start, it just would require too much work for something that's really minor - as you can already have a Polish-Teutonic war in 1444 if you want.
Greetings from Poland.
