I've seen alot of people request combat, but something like RAIDS would be a great and fun mechanic to this game.
Raiders come to attack/destory/burn your village while your villagers can be assigned as soldiers. The keep could make a temporary safeplace for your population while you fight off the invasion. The recently added watchtowers are allready great for defence!
I get that adding combat might mean alot of work but it would add so much new building strategy, fun and replayablity to the game!
Maybe once your get your keep up, you can assign a king (?!) and the invasions can start.