Actually, I have something like that in my mod. Whenever a city grows in size, it'll expand to nearby tiles on the world map. And when its nuked or destroyed, those city expansion will become ruins. Even though the city itself never becomes a ruin, its still kinda neat to see city expansion ruins all over the place.
Okay, I only just recently completed the mod and have not gotten to the point where I can nuke cities yet, but I can't wait to get nukes, so I can start seeing some city ruins.