@d4m0r3d I know it's a game and I am all for games not being 100% realistic because they have to be fun.
What I ment is that there are game physics...water and wind push your ship even with sails up, wind hitting your sails different ways changes how fast you sail, etc. I don't know how they programmed the sails. If in the programing sails are just a square area on your masts that dosen't neccessary match up with what we see on screen (like how everyone has the same sized hitbox no matter how thin or big their pirate is) than it should be easy to add different shaped sails and have them behave the same way. If the programed "sailbox" actually conforms to the square sails than changing the shape of the sails will probably change how the ships handle, which would require much more balancing and testing.
I would be happy with either new surface cosmetics that just made our ships look like different styles of ship or with whole new ships that had the same crew and weapon sizes, but had new advantages drawbacks with how they handled. I was just pointing out that doing so may be more complicated than it actually seems.