Oh captain my captain!
Mostly aimed at PvP servers.
The naval combat that exists today is purely brawling next to each other when sitting in a boat.
Maybe implementing a Cannon , that can be loaded in larger ships such as Carval / Cog and manned individually by crew members and use sort of the same combat system such as arrows being shot.
Should do less damage than catapults and trebuchets on buildings though to encourage players to go on land and continue their attack. Do not prevent cannons from being fired from only ships though as they would make a great addition to coast deeds defences against what ? Ships of course!