I'm finally making some headway on my mod. I've got the CulturePerPopulation component completed! Now monuments, Opera Houses, and Museums all add culture based on the city's population! As do many of the other unique buildings that also add culture. Everyone has been balanced to provide the same amount of culture for a city of 5. For larger cities, they'll produce even more culture!
Nice. Surprised that you are the first person to come out with this functionality.
This includes the XML to update building culture levels including a brand new XML table, new help texts to inform about income these buildings provide, as well as Lua script to update each city's culture generation each turn in case it has grown.
Does this mean if a building gives X Gold/Culture/etc per pop that a tooltip tells you how much that will be when you are looking to build it? That would rock.