After the AI was informed on the requirements to form Prussia, the next step should be an update to Muscovy that will faithfully keep one of the Russian minors, usually Ryazan, allied for the length of the game and block itself from forming Russia.
I like this, with the added thought that maybe this is how all cultural unions should work. Owning certain cities could certainly add to legitimacy, but if I own 90% of, say, Italy, what does it matter if I don't own Milan or Firenze? Especially if France or Austria holds it only to keep me from tag-switching.I would like to change requirements to form Russia. Instead of certain cities it could be Moscow, Novgorod + at least 25 provinces with russian culture group or in russian region or maybe at least 5 provinces from few groups (Muscovite, Novogrodian, Ryazanan) like mission Unite the Mongols. It's to easy to prevent Russia from forming by conquering or vassalizing Ryazan.
Could be an either/or thing: "Owns [12 important cities]" OR "Owns [1 of those cities] and [number of provinces scaled to the size of the culture]." So for Germany, for example, you could require either all the important cities, as now, or one of them and let's say 75% of the North/South German Regions.I like this, with the added thought that maybe this is how all cultural unions should work. Owning certain cities could certainly add to legitimacy, but if I own 90% of, say, Italy, what does it matter if I don't own Milan or Firenze? Especially if France or Austria holds it only to keep me from tag-switching.