cultural shifts
My current set of random events for my Free Destiny mod has two random events that change province cultures randomly.
1) Migration and Assimilation - one of your provinces shifts to your 1st state culture. Based loosely on places like Sardinia (which was sort of Iberian for a while) and the Alsace-Lorraine (which has a blend of German and French cultures to this day). This is implemented by:
command = { type = provinceculture which = -1 value = -1 }
2) Genocide - based loosely on Torqumada, which for a high revolt, stability, and tax/manpower loss allows you to shift a culture.
I don't see why shifting cultures would cost you money? You can't pay to change people's ways. You can either allow them to fluctuate over time, or you can ruthlessly exterminate and ban people's cultural ways, but you can't just buy it.
The EU2 engine provides no way to have a culture shift after a period of time under your control. My random events are perhaps too much for some people. After all, how likely is it for the Albanians to adopt Italian culture? Not likely, but under Venice's control, that's what happened in my last game. Still, I saw only 2 provinces with changed cultures (1 baltic one under the Teutons and albania) after 50 years, not bad, and not terribly unreasonable.