[snipped...]
Okay, okay.... back on topic. What game topics to add to an expansion? How about population migration? When a neighboring civ is exerting cultural pressure, perhaps the population of the closest city might decline and add itself to a city in the neighboring civ.
That is an interesting idea. It would probably make a lot of players aggravated though, but it is somewhat "realistic" and you would have to pay attention to culture. I tend to use culture only enough to claim my borders with only a very occasional culture battle to get a good resource (maybe twice).
As a balance, it could be made into a slight "double-edged sword" for the benefiting civ. A smaller culture clash between the new migrants would still exist since they are not "becoming" say French so there could be small unhappiness effects until they are fully assimilated. Also, until then if there were war between the two empires, the yet to be assimilated population might feel a little nationalistic nostalgia and become unhappy.