Your mast damage and weather engine is truly impressive. I have two feature ideas (one probably easy, one probably really hard) in that department:
Make topmasts break randomly, not based on a threshold. Currently the masts seem to carry away very consistently based on wind strength. I recommend changing it to a percent chance over time, so that it takes a few minutes on average. That will make it possible to capsize in a storm, which makes things much more exciting. You could also make it more likely that the courses will blow out, rather than taking down the whole lower mast.
Also, large waves could generate big foam objects to simulate breaking crests. You could give these the ability to capsize a ship if struck right on the beam, and apply turning force if pooped. That would really make storms terrifying. The probability of breaking could increase when wind is against the swell direction.
Also, do you think there's any latitude for plugging in more detailed sections of coastline?