This is just an idea, but I suppose this is the "Ideas" section of the forum...
Anyway, I think it would be a great idea to be able to establish Political borders through treaties once you hit the reniassance era. It could be a dashed line the color of your civ or something. I think this would make the game a good bit more realistic. It would stop civs from founding cities in between your own late-game too... You could either have to sign an open borders treaty to cross the political borders, or there could be a similar set up to the way that is handled with city states, with a violation of a civ's borders upsetting them and leading to diplomatic ramifications. In the latter case, open borders would only be needed to cross into a city's definite (controlled) territory.
Take Russia, for instance. The real Russia, not Civ V Russia. They have controlled Siberia for centuries, but have hardly settled it at all, even today. Yet you don't see China founding cities there. I think Civ V should have a similar mechanic. Just an idea, though...
Anyway, I think it would be a great idea to be able to establish Political borders through treaties once you hit the reniassance era. It could be a dashed line the color of your civ or something. I think this would make the game a good bit more realistic. It would stop civs from founding cities in between your own late-game too... You could either have to sign an open borders treaty to cross the political borders, or there could be a similar set up to the way that is handled with city states, with a violation of a civ's borders upsetting them and leading to diplomatic ramifications. In the latter case, open borders would only be needed to cross into a city's definite (controlled) territory.
Take Russia, for instance. The real Russia, not Civ V Russia. They have controlled Siberia for centuries, but have hardly settled it at all, even today. Yet you don't see China founding cities there. I think Civ V should have a similar mechanic. Just an idea, though...