Oh wait clarification, my idea requires a reworking of espionage (something that I'm not sure will occur) to a more macroscale, like a seperate espionage screen, not just units. This is because for a player to be able to take advantage quickly of a revolt, there little chance of having a spy nearby waiting, and within moving distance to add to the enemies civ's problems
It would be nice if spies could incite riots, to stop a city functioning,
they could be cheap but have a chance of capture..
even diplomats could do this but it wouldn't work if the diplo died each riot he did.
I guess a less civilised culture would riot more, just out of their nature, not from unhappiness..