I love the game and the gameplay from it! The sprites and islands are very pleasing to the eye. One of the only complaints I would have is the stockpiling mechanics, whenever I try to bring out the airships I can only make 20 at a time. Maybe make a Stockpile building to try and balance it out as space is at a premium? Could reward those with large territories. Another thing I would want to see would be hotkeys for the buildings; a simple 1-10 could work. Very tedious to move my mouse up and down.
A suggestion, please don't feel inclined to do so, would be a diplomacy system. Like with the random enemy settlements instead of just attacking them, you could bring them into your 'sphere of influence' as a sort of out post for expansion. Maybe you could bring out other expanding AIs to spice up the game and the random enemies could be a barbarian from the CIV games? Thanks for reading this wall of text.