Biggest problem as LHeureux said is someone to make them
Not 100% sure how they are going to be ingame, one option is to have them "player sailable" but their isn't much one could really do other than sail it up to a point in range of the enemy ground forces then use its cannon to blast the **** out of them (which isn't totally unrealistic)
Also isn't impossible, the Battleships mod had controllable ships, but they had to be low poly in order for them to work, but probably could have more detail and still be able to export them as a single object.
The other option is to have them like the Atlantic Conveyor, ie, stationary, but having usable weapons on them.