I have another idea for cannons: HESH (or High-Explosive Squash Head) shell firing cannons. These cannons can fire every 3.5 seconds, and can penetrate 2 (or 3, depending if the first block is a wedge block) armour blocks, before detonating in a 3x2 (3 long, 2 wide) radius, leaving some fire behind. You can nerf the reload if it proves too OP, and if possible, only large-size cannons, but you can do whatever you prefer 🙂
Overall, this mod is shaping out to be quite good. Wouldn't surprise me if sooner than later i begin using it. Great job 🙂