I once had an idea for a version where hit points were equivalent to firepower, so:
Battleship 4-4-2 (4 hp)
Cruiser 3-3-3 (3 hp)
Destroyers 2-2-2 (2 hp)
Each ships would have the appropriate number of gun turrets, which can be removed when a hit is taken to indicate damage and reduced firepower.
Two hits slows down a BB, one a destroyer.
