If you dead that then all nobles in a war commanding archers are significantly richer due to the fact there archers arent dying as often since they are retreating thus Tom's balance comment.
This is true in general anyway. Even when you are winning battles infantry are going to have more losses in general to replace. But I agree anything that makes archer more survivable will tip the system. We will end up with stupid things like armies with a few infantry units to absorb damage for a few turns, then your archer retreat with next to no loss. Rinse and repeat next turn until the enemy is finally brought low by arrows.
The idea of a orderly retreat after infantry are dead just doesn't really gel with me. There are reasons why in so many battle the majority of deaths were suffered AFTER the army left the field of battle. Don't archers already attempt to pull back from the melee lines? That should be more then enough, if you want something more then set archers to have low withdraw settings.
