An interesting dynamic to the gameplay to add would be fire.
Fire could be used for tactics like burning down trees, a wooden fort ,Ships and Sails, houses or fields. Like you would use a torch to set something on fire or anything else that would start a fire. In addition a fire could also occur during a battle from an explosion or lightning or other event. In addition to combat this the ability to put out a fire out you could pick up a bucket with water or stomp it out if it just began.v