Crews on this ship could be restricted to one weapon, except maybe the captain and their first mate or something (captaincy update? where are you? Lol)
Respawn timers would be longer based on crew size, ammo count could be 3 before reload instead of 5, idc how they justify these things as we can shoot ourselves out of cannons. Point is they could make it balanced if they made some exceptions to their level playing ground per singular player, which adding this ship would itself do so imo these suggestions would be fine. Who needs 2 weapons when you can fire a cannon from cover below decks? Be another case of teamwork being key and i can still see the pro sloops sinking these behemoths in my head as we speak haha.
Aswell as this the ship would be slow to accelerate and decelerate, have a decent top speed but be completely unwieldy to control when turning at speed especially, take damage and not stop as fast when using anchor at full speed, etc, and even galleons should be able to run circles around it.
They could make this work they would just need to alert players taking this option that they are making a lot of concessions similar to how the sloop has a warning.
Though the world itself and the weapon set and sandbox elements like powder kegs abd questing and npc and life in the world all should take priority over the next new ship, unless it is a ship tied into an economy/world update such as described in @Starship42 ‘s post about abandoned ships.
My description of an ideal man of war:
4 decks
Top deck has the 3 sails that need 2 people to be turned but otherwise are similar to the other ships, and 2 cannons one tilted fore and one aft, on each side, still mainly facing the port and starboard.
2nd deck has 3 cannon on each side that fire altogether at once, with long reload time that requires each to be loaded manually, and the fuse connected, with a timer similar to powder kegs. Maybe 3 seconds not 5. also requires cooperation to aim from the top deck. Minimal swivel action for these through the cannonports and almost no view at all through them. Cannonball barrels here x2 and one above deck ( they can hold so many now so no need for a lot of them)
3rd deck cooking and sleeping quarters for the crew, cargo space, vanity and equipment chests and weapon and ammo crates. Banana/food barrel.
4th deck map room and voyage voting table, navigation room
Basically that also holds plank barrels and the larger than normal brig (alpha style galleon brig at the end)
There would be multiple ladders and ways to board and even an extra ladder/harch to below decks from inside a large captains cabin below the helm similar to the galleon, possibly voyage table in here rather than near the map area.
They could make this work.