I've been playing the game for an ok 30 hours by now. What I've noticed during campaigns/conquest games is that oceans land vessels have to go across to attack, and unguarded by airships can easily be wiped out. And I've been thinking about a concept for naval vessels. Basically like an airship or land vehicle but floats and moves on the water. They can provide a key role in escorting land vessels moving across waters. Customizable and able to be built like an airship but with buoyancy mechanics, too heavy you'll sink, too light you'll be tapping the surface with the bottom of your vessel. Armor can very size can very. They could be that very similar to airships like i said already but just, floating on water. And with them being added could maybe be some heavier naval guns that weigh a good amount, consume a large amount of ammo and fire slowly but pack a hefty punch, along with smaller AA guns but those can be optional since regular land/airship weapons could also take both roles. Hole point of them being added (if this topic/suggestion is to be picked up) is just an alternative way for escorting land vessels across water and maybe even intercepting enemy transports across water, which could mean to hole new way for strategy against opponents.
I plan to add naval vessels in an expansion after the 1.0 release. It makes a lot of sense to have them, but I felt that I needed to draw a line in terms of initial features.