imo, champions should be changed. their power doesn't scale very well, as even a extremely well-equipped level 10 hero can be instakilled by unit stacks and some of the nastier wilderness monsters. perhaps make them start out as small-time rat hunting adventurers, and as they get better their power scales on a large curve. starting on a level slightly above average fighter, and on the higher levels be a magically equipped combat master, able to take on 20 guys all by themselves, inspiring nearby allies, with a variety of special attacks and abilities. think gil-galad. their passive garrison side-effects should also drastically increase in this way, perhaps as they sit in a city, using them.