My ideas: Cavalry: make a horse and cavalier as separate units, with their own HP and experience, and let the soldier dismount from horse and fight on foot (for example, when horse is wounded) or mount the other horse. For infantry: tell the archer to 'holster' his bow and use the short sword, to make him a little weaker light footman (but anyway more efficient in close combat than regular archer), also this could work for pikeman, when he has to deal with non-mounted enemies. What do you think about it?