Revolutionist_8
King
I really hope that this idea get implemented in the [WIP] Cities in Development.
Well, I tried Revolutions some time ago, and the idea is more or less already in Cities in Development: if the Loyalty of your city falls down, it will contribute towards a meter, which, when filled, can spawn rebels or even the city itself can defect to Barbarians. It's really well polished and balanced, and it's incredibly fun! ^_^