City Morale?

Back in the day (hehe), Master of Magic had a morale system.  Galactic Civilizations had happiness for civs, I think it would be cool to link resource items (spices, salt, silk, whatever) to happinses and be able to flip other cities with enough influence surrounding them.  Perhaps cities could go neutral or even change sides based on bad morale and outside influence.

You could also have happiness affecting spells.

Just a thought.