I recently captured an enemy city at the fringes of his empire. This city was a good ways away from his other cities but he had built up quite a bit of cultural borders around it. And so, after taking it I only had 1 plot to work with besides the city plot, which got me to wondering just how was he maintaining control of all of "my" other city plots. So, I started thinking about how borders are calculated and if any thing could be done to make it more fun and or realistic.
It seems to me that if I have units present and he doesn't I should be able to control those borders. So, perhaps that could be a rule, if you have a Military presence in times of war, you control the borders around captured cities. There could also be certain Administrative buildings or Civics that can do this automatically and you can put your units to work inside the city, or move them out for military actions elsewhere and you would not loose your borders. However, you would need to build up cultural influence quickly as in times of peace those borders could then revert back to their owner. And perhaps we could add a new Diplomacy option for Peace in that you can also put on the table to "Maintain Current Borders" and thus, the enemy looses all rights to his borders and they become yours.
Also, could there be changes to how borders are expanded? Could we have improvements, such as Watch Towers, that are built and when they have active military units present they exert a border influence. These military influenced borders could be shaded differently so that you can tell them apart so you know you must keep a military presence there to sustain the borders.
In times of peace, if both sides have a manned Watch Tower present then normal cultural calculations apply. In times of war, however, the borders are changed according to military presence. If I move a unit onto a plot that is controlled by an enemy Watch Tower, my unit gains control of that plot and I would keep control of it, even if it is unoccupied, until he sends out a unit to take that control back.
Anyway, that is my initial ideas on this subject
