A few things that would make OW more fun:
being able to deactivate auto skipper
being able to take a sight with your sextant to know (approximately) where you are
more bad weather (bigger waves)
ship customisation (name, paint, flags...)
sailors singing (that was just awesome in Black Flag!)
sea life (whales surfacing, dolphins swimming around the ship, sharks...)
I know there are other priorities, but those things would be really nice