Add some crafting like use iron to make longer cannons, or lit bombs to be fired from cannons, something that can improve your defenses. Maybe add some crafting things to equip troops, like bulletproof barrels, or a battle axe for brutes (I dunno). If they add in-battle power ups, then you could craft them. Perks like blacksmith can serve some other purpose too. Craft like Minecraft PE, not PC to make it easier.
