First off, I have to say I enjoy using champions despite their late game effectiveness. With that said there are some issues with champions in the current build that I would like to discuss along with some suggestions.

Attributes

Intelligence- IIRC this attribute only affects spell effectiveness. It would be nice if this could be used by non-caster characters. One possible use would be an increased chance to bypass some armor or defense. This could represent the character being smart enough to find a way through a unit's defenses.

Charisma: IIRC this attribute only matters for the sovereign. It affects costs to recruit champions and does little else. Well since leaders need charisma to rally and marshal their forces effectively, maybe charisma could be used to give a boost to morale for the army (only take the highest charisma and that character is the "leader").

Late Game Vulnerability

From what I've seen, the late game vulnerability of champions stems from a few issues:

1. Combined Soldiers: The upgraded units sizes (Squads, teams etc) have the soldiers add their attack and defense to make a total attack and defense. This has been discussed before but I feel it is the major reason champions loose their effectiveness. Take a basic soldier with 5 attack and 0 def. This soldier would be very inexpensive to produce. If in a unit of size 12, these peasants would have 60 attack. Even with the best armor in the game, a champion could not hope to have 60 def unless you extensively leveled that champions dexterity. If the combined units were treated as 12 of the individual soldier, the champions would fair better. After all why would a knight in full plate be slain by 12 peasants with sticks (maybe a hundred but certainly not 12).
2. On Their Own: Champions take up the same space as a company of other soldiers. While I think a champion should be able to roam around on their own in a battle, they ought to be able to lead other soldiers. How this could work is as follows. The champions gets an action to join a unit. Upon joining the unit, the champion can no longer be singled out. However, damage that hits the unit would also be divided towards the champion. SO if there is a unit of 10 soldiers + a champion, the champion would get 1/11th of all damage (some recalculation needed as the champion would probably have a different def than the rest of the soldiers)

Equipment

Equipping a champion can be very costly. And I have to ask this simple question. If I can use my metal resource to give my soldiers armor, why can't I make that same armor for my champions? The same goes for weapons. Right now, a champion equipped the same as a soldier is several times more expensive without anywhere near the same rate of return; a champion will only be slightly more powerful than a grunt.

So I propose the following change. Allow champions to get equipment in the same manner as a regular soldiers. Let a building like a blacksmith be able to be visited like a merchant shop. This is where a champion could purchase all of their "normal" equipment available to any soldier. The merchant could carry all of the supplies that are "champion only".

Suggestions

1. Dueling: Coupled with my suggestion on Champions leading forces, I would add in a small mechanic, Champion Dueling. Basically a champion could call out another champion that in melee range or if they are both in range (two casters/archers). When this happens, basically the two characters fight until one is beaten and no one else can interfere.  Of course the challenge can be turned down which would have  negative impact on morale because your troops would think you are a coward.
   
2. Feats: I would like to see feats added to champions. Every so many levels a champion could get a feat which would give them a bonus or special ability. These would function just like the abilities monsters have except now we could get something similar. This would add some flavor to the champions.
3. Caster Gear: Mages could use some equipment that helps with mana regeneration. After a couple of spells, my mages are depleted for dozes of strategic game turns which is way too long.

Anyway please discuss your thoughts and ideas on how to make champions more complete and balanced.