Really cool game! reminded me a little of "age of war". It was fun to build structures but it was pretty hard to keep them intact while fighting off the enemy. Maybe the pieces could have a structural integrity component? so that they don't die immediately from the canon. You could also add a way to repair components. I think it would be cool if the islands were bigger to allow for more complex structures and opening it up for ships damaging the structure without that being too overpowered.
Better player feedback in the form of sound and better hit effects could have gone a long way and the airship was confusing. I was thinking it would just be a slow bomber run that does damage to everything.