Abandon City
Have an unwanted sub? See a new one that you want but don’t have an open slot? With the abandon city feature, you can give up ownership of your unwanted sub to make room for that new one that you want. The abandoned city will remain on the map for a little while to allow it to be farmed or captured by other players. After a set period of time (TBD), a self destruct mode will be activated and the city will disappear from the map. This will keep the map from getting cluttered with unwanted sub cities.
Also included in the abandon city feature should be an improvement to scouting. Perhaps this could be in the form of a tech upgrade. A scout of a city will reveal the level of the buildings in the city, with the appropriate scouting tech level.