All your ships have a usage for something else but there is one thing missing. Missing type of ships in your collection are maintaining ships. Ships which will refuel all boats/ships in open water. Such type of ships would be handy to make long use of ships without going back to the port just to refuel/respawn because someone can use ships ... not really safe.

It is possible to use oil tankers from someone eles but i would like to see such ship which is in same style as your creactions.