I'm toying with the idea of adding carronades to the mix. It should be an easy addition, since I roll d6 dice to determine the available crews/weapons for each round (a 5 or 6 is a cannon), if boxcars (2 d6's) are rolled you get one carronade, not two cannons. The carronade causes two damage points, rather than only one as for a regular cannon. Also possibly allowing a carronade to take out a regular cannon - not sure about that yet. I can see numerous optional rules that could possibly make the game more interesting.
Also possibly adding event/fate cards to add some uncertainty to the game. What's your thoughts on that?