I think ships need to be customizable just like land units.  You shouls be able to change out faster or slower masts for movement, lightly armed or heavily armed crewmen, or weapons such as onboard catapults and ballistae.  Maybe even have some ships with spellcasters to increase movement or help in combat with healing or fighting.

Also, I think may have been suggested, but there needs to be different types of fish, shrimp, and crab resources out in the ocean that could be harvested for food.  Also trade route establishing ships as sea trade and river trade is extremely important for medieval type cultures like this game.  Ships can then be outfitted with fishing equipment ot extra cargo space for trade.

I feel the whole maritime part of the game is severely lacking and so far seems completely ignored.  That is just wrong as the sea and rivers should be important sources of resources and tarnsportation. 

I wonder if this idea would be considered a new feature or if it is easy to implement in the current game system?  I can't express enough how much I think this aspect of the game needs to be more developed.