So some of the devs have bounced around the idea of having heroes as governors, but I personally would not want them to sit around in a city to give them bonuses. Instead, I had another fun idea to throw into the mix...
If a hero is governing a city, the city gets benefits based on the heroes exploits.
Basically, once you get high enough on the adventuring tree, there would be a monument dedicated to that hero in the city. For instance:
Billy the Ranger has completed numerous wilderness quests and has managed to capture all manners of unique animals. His monument gives bonuses to all rangers and animal tamers trained in the city...
Samuel the Sorcerer has completed all kinds of special magical quests and has procured many powerful magical artifacts during his career. His monument gives bonuses to magic based city production.
Ricky the City Razer and Freaking Lunatic has burned a dozen cities and even slaughtered farmer Joe and his entire family after farmer Joe sneezed. His monument scares the shit out of people, and every person in the city is very, very well behaved.
When the hero dies, the monument can no longer grow in bonuses, but remains in the city unless a new hero governs the city. This method has the advantages of not having to leave your hero in the city to govern it. Instead, the city benefits from the success of the hero while he/she adventures.