So i was thinking about the same thing that Andromeda and Jason have. 1 gives extra loot when attacking, 1 increases the resources in the city it is in.
Basically, the idea is a Hero which will passively increase the favor you get in that city for that god, as long as it is in the city. So...
When launching an attack there is a select all button that selects all units in the city to launch on an attack. Missing from this selection are a cities hero's. For many attacks this isn't an issue, but when timing attacks it takes too much time to select the hero for an attack leaving players...