Very nice and a real coincidence. I bought half a dozen of these tinyurl.com/wood-pirate-ship recently, from American Science and surplus. Very cheap and simplistic wooden pirate ship models to assemble.
But after I got them, it struck me that they could be made into "modular" sailing vessels, that could be painted in a general way, and then be blue-tacked together with additional parts to make a great variety of ships.
Possible variants:
Sudan War riverboat: much like what you have done. Remove the sails and fore and stern castles, mount a superstructure assembly from blocks, (as you have), a toy cannon (probably a small field gun in my case, as these were often used on such makeshift warships), smokestacks made from wooden spools, cotton wool smoke, k'nex block paddle wheels tinyurl.com/knex-pieces, a few flags, etc.
Ironclad: Similar to but simpler than the above, with turrets made out of some type of small cylinder and dowel rod.
Ancient galley or Viking longship: banks of oars on some type of angled metal on each side with kitchen matches for oars and thumbtacks for shields appropriately mounted and painted.
Modern drug-lord boats: I think I could get a speedboat full of drug runners out of the fo' and stern castles, while the main hull could easily be a Coast Guard cutter with the appropriate turret, etc.
Of course, there would be problems, but some clever painting could overcome many of them. For instance, paint the sides of the hull black, the tops brown and the bottoms gray. Now you have somethinge that works as a wooden ship, (brown side up) or as a more modern iron ship (gray side up), with the assumption that black 'walls' on a ship can be fairly universal.
Aas you can see, you've inspired me. I'll make a video when I have these done.