I say a building to fix these things. A special building 1 per empire that will have a chance of removing an injury each turn. This way a highly wounded champion could play governor and get healed to be and adventurer again. Makes it a mid to late game construction at a decent cost, not relying on mana, so the AI will be able to utilize it with little coaxing.

I would prefer a fixed turn limit for each injury. The chance thing was something I know could be easily modded at present. Do you know if with the current tools that a fixed turn limit on indvidual injuries could be implemeneted right now?

I also think it should be also remove only the earliest injury and as injuries are removed move down the line. As old wounds are hard to heal. Notifications are a must in this area so people know when the hero has been healed.

Ideally, I would suggest build a building which adds a new action for champions on their bar called heal injury (or something) and incapacitate the hero while the injury is being healed. The biggest problem here is getting the AI to use such a feature.

I just thought of a random event... a prophet appears preaching kindness and goodness to all. Send your champions to visit his humble house. When you do that champion is healed of all afflictions and injuries.

That's what I suspected from my knowledge of the .xml. Thus, expansion time is needed for this good feature. But for now time a small chance 5% each turn to remove ALL injuries on the champion would be the only way to go for modding at the moment.

Can you get the AI to use this?

Yes. I just make it think it is a really powerful enchantment.