Currently behavior in waves is just fine. You wouldn't expect the ship to capsize because the game's waves are never breaking. So if it isn't possible to make the waves occasionally steeper, it might be worth faking it somehow with foam FX and a buoyancy object or something.
I think of waves in a strong storm as a numbers game where you might get unlucky and have one break right on top of you. So in gameplay terms, being beam on to the seas would expose you to a possible knockdown.
Also, given the whole-world capabilities of the game, probably the most important feature is windowed mode (so it can run in the background while unpaused) and a save function. Unity will provide that, right?