I don't really want to see natural regen out in the field unless it's being granted by an item, first aid skill, or resting at some ruins or constructed fort/campsite. Magic of course being another option, but I was just limiting it to basic units. If you've chosen to go adventuring in the wild, it should be an incentive to return to town to rest up and heal.
A sovereign of whatever faction ends up possibly being connected to life magic could be an exception, possessing an innate power to self-heal.
