Granted I haven't played in a long time so sorry for the newbish question, but if you place a Champion in a city, does he/she at any point start to gain XP inside it?
I have a champ that I decided to take the path of governor trait and noticed the champ is not gaining XP while inside the City after a few turns, thus kind of defeats the whole purpose of being the "governor" in a way, unless I'm missing something with buildings later on that can make champs gain XP while being inside a city.
If for some reason you haven't thought of this, perhaps it could be a suggestion meaning if decide to give the Champs the "Path of Governor" trait, than he/she should get XP while being in a city, but than at same time nerf their attacks/defense so it won't be OP once that trait is aquired. (thus making it an easy way to level, since at the end day the Champ should be kind of useless in combat if you pursue that path)