This is purely advantageous for large countries. Why would you want to buff them even more? I like the over time part, but in my opinion it should depend on other factors: First, the %of that culture of YOUR total dev). Furthermore, one could think of a bonus for historical friendships and a malus for historical enemies. It could also be influenced by your current diplomatic relation with countries of that primary culture.How about this, whenever you conquer a province of a brand new culture the province gets a cultural acceptance modifier from -100%-0% affecting things like manpower etc. This would tick from -100% to 0% over time. Now if you make the value of that tick proportional to how much of that culture you control (as a % of total dev), something like Ottomans conquering Albania could become accepted quickly whereas France conquering Kent would almost never be accepted without the French conquering more English territory.