I have an idea for city conquest that can simulate population exodus during war.
What if every time a city is conquered all the cities around it (Depending on the size of the conquered city of course) gets one extra population point. But the population point, can not be used to do anything, e.g. farm land or be a entertainer. This way the game simulates very simply the idea of refugees. They act as a drain on the city they run to and cannot add anything to that city. Though I believe that over set time period they should be change to a normal citizen.