this isnt a very important change but i think the borders should expand after 6 or 12 population instead of having to spend money on cultural buildings.It should do this because ive seen some ai cities with a population of 15 or 16 and they still have a one square border soo it can get pretty crowded :wallbash:

The only time I have ever seen a city of that size without any expansion is a newly captured city. Other then that, what are you building if you have not one improvement that generates culture?