Well i can imagen that armies will get unconscious first and unable to continue the fight. If they are left alone they can survive a fight if it doesn't take too long. As long as the fight continues they are loosing health. After a fight they can be healt again. Maybe all health potions in a battle should be tempararely, so after the fight the real healing takes some time. It makes sure that when you cannot encounter several enemies after each other without consequenses.

When you win a fight you can decide to kill all enemies that are unconsious. Take them prisoner (and become a resource) or let them free to improve your standing with the enemy.

(Field-)Hospitals should increase the health regeneration

Thinking about prisoners of war.

Would be nice if we can get the armor etc from a battlefield. And depending on the health of the prisoner we can take his weapons, helmets etc

From a dead enemy the quality of the armor etc would be very low (it is damaged in the battle)

Or maybe add some quality points into the equipment. During battles the quality decreases. You can learn you're footmen to repair their own stuff or add a forge to the army. Equipment taken from an enemy can only be repaired if you have the right knowledge.

Example: a troop of barbarians attacks a lonely soldier with an excellent equipment. They win and one is taking its equipment but can only use it at 50% potential because he lacks the knowledge to handle them properly. (maybe he learns from every battle?) He is also not able to repair the equipment so it is becoming less functional after a few battles. Until the moment he had to throw it away because it became too damaged.

In fact knowledge is a resource affecting several factors in an army. And people can be enhanced with this resource to use it for their own equipment

Hehe, funny I was reading about something similar yesterday in another forums.

In "realistic" combat units break or are "destroyed" around 30% casualities, but after the battle those "destroyed" units are recoverable with 30-40% losses. Unless the enemy fields light units, skirmishers, cavalry and so on to be able to catch those fleeing units.

That gives different roles to different types of units (fielding heavy units is important to win the battle and fielding light units is important to make sure you kill/capture as many people as possible when the enemy routs).