Obviously not exactly a family friendly game, but the dev has posted the entire, unobfuscated source code, so modding it should be significantly easier than other games.
The pure chaos would be amazing.
In the current state of the game, it seems like the devs are leaning towards the idea of one class of ship per biome. The ketch for the coastal jungle, the brigantine for the foothills, frigate for the swamp, and the planned galeon for the ashlands.
While this is nice and fits well, it does feel like some more diversity, such as what we already have with our weapons, would be nice.
Some ideas I had were:
The sloop. Basically an upgraded version of the small boat. Faster, has some small cannons and storage space. Important to note is that it would be usable in addition to your boat/flagship, so it could be used to zip around islands or go pick up loot where you died without getting battered around by the waves in your small boat.
Ironclad. A very slow, but extremely durable ship. Great for taking on those 1v10s, but not so much for jumping between islands.
Submarine. Less u-boat and more Nautilus. Has a ram torpedo (basically an explosive charge on the end of a long spear) that can only be reloaded while surfaced. Perfect for devasting single target damage and avoiding detection. Could also be required to access under water areas like sunken shipwrecks or drowned lairs.
Caravel. Fast and nimble, but lightly armed. A known trading ship. Blackbeards pirates will attempt to board you after disabling you rather than sink you outright.
Hauler. A giant, incredibly slow ship. Designed mainly for moving massive amounts of resources between bases without the need to teleport 100 times.
These new ships would be unlocked through a new faction, the shipwrights. This faction would also sell you additional shipbuilding related base pieces like drydock gates and slipways, but most importantly, they would sell additional ship upgrades, more crew, and captains. Hiring on more crew and captains would be expensive, but each additional crew you hire would be an extra ship to sail alongside you in your fleet. The caveat is that your fleet cannot be teleported, they must sail alongside you.