As others have said Rare wants everyone on generally equal playing terms so many of these ideas likely wouldn't surface in game. That being said, I shall still give feedback on the ideas while building upon them.
Hull: It could also take on aspects like Pirates of the Caribbean Online. The reinforced hull would also slow down the ship somewhat. It would be more about endurance. The lighter hull would allow it to also sail faster, still take the increased damage from cannon fire, but also maybe make it so it can be knocked about by the waves more like how a sloop is in a storm.
Cannons: For Heavy cannons I would probably allow them to fire farther instead of that splash damage radius upgrade, but keep the slower reload. Maybe also slow the speed of angling it, but that would have to be tested for balance. "Shotgun", firstly i'd do away with that name and just call it what it is, Grape-shot*. Given the damage scale of small-medium-large hole for ship hulls these would only do small hole-quantities of damage, would lack accuracy, but could pepper a hull. I wouldn't let them cause fires though as that would likely be a bit to over powered.
*Grape-shot could certainly be added as a new ammo type though. We did just get the firebombs that can be fired. Maybe there could also be a heavy harpoon ammo for the broadside cannons that could be stronger than our round-shot against Krakens and Megalodons (could also lead to future beasties being added such as my suggested "Fogbell", a giant Wrecker/Angler).
Sails: I would likely make one that is more heavily reliant upon the winds. It would likely be harder to raise when in the wind requiring players to angle them first and then raise to raise them faster. As for the maneuverability sails, the mixture of those two traits don't really make as much sense.
Front: I'd say the chase cannons should instead be swivel guns and use the same ammo as our rifles requiring us to reload from our own pockets. It would incentivize the use of the new ammo crate (which they are addressing why it doesn't spawn). Mortar, this one is a bit tricky. I wouldn't really be able to see one being used by the in-game sloops given their size. A brig could maybe use one, but I could see it being knocked about/rocked by the firing. I could certainly see a galleon have one. For balancing I would likely toss in some kind of fuse or "timer" once ignited with a reload speed the same as repairing a large or medium hole on a galleon. A ram, I could see this be somewhat useful especially if it could reduce damage caused by hitting the bow of the ship on say a sandbar (in terms of non-combat uses) or rock. I could maybe then add some form of repair mechanic to it. Maybe two planks on either side where the harpoons would've been as a way to reinforce/repair it after heavy use.
