It would add a slight amount of complexity but it would also add the ability to make the governor more useful in a single city immediately instead of just getting it to level 6 and parking it somewhere.  Mainly it is more of a way to add a layer of depth the game does not have, a way to add loyalty and espionage by way of sabotaging loyalty through spells or abilities.  Maybe add some more non combat abilities to the game say for the assassin class could have an ability to undermine (read this as a city debuff) loyalty as well. 

I suppose you could simply have an unrest penalty if you have a lot of cities.  I can't remember if it already did that or not.

All Empires (Sion) and Altar (Henchmen) can train "governors."  When trained by a fortress with Command Post = +3 levels, so that's 5% (base champion) + 15% (Commander) + 10% (Administrator 1) + 10% (Administrator 2) = 40% Unrest reduction when just popped out of the unit factory.  You can give them the "Veteran" trait for another +1, but it raises the wages and is generally overkill.

I generally make a unit called "Governor" just for this purpose for Empires/Altar.  You don't expect them to be in any decisive battles, so you don't even need to equip them (though I usually give them a horse for mobility's sake.)