To improve the feeling we can impact the world by winning (or loosing) missions, it would be nice to have a simple gauge in the city tool tip.
In peace time, the gauge would show the city prosperity. It will indicate when the city will repair building or when they will go in ruin.
In crisis time, the gauge indicate when the city will be destroyed (or flip side during noble war).
It seems easy to code and could really reinforce the feeling player have toward some part of the map.