Basically saw that people have larger multiplayer mods for settlements, pvp, island sizes, etc.
But what of the actual movement between map nodes and the risk-reward factor of actual ocean maps and biomes?

1) Ocean biome tiles - You cannot landfill them, your boats don't work well in them, oceans are suppose to be hazardous to travel with vanilla content. For instance those boats and travel related gear that promotes more map tiles ranges? Ocean tiles would negate all of that, only ships can have buffs to travel past those tiles. Boats moves slower in these 'rough water' tiles than ships do, which makes them prime targets for cannon fire.

2) Ocean related tech tree - You construct ships which are bigger than boats, but you do not equip them, rather it's a entity that is like a NPC but exists persistently and allow players and NPC to ride in them (stored in a sense). Cannons, harpoons, storage slots for inventory and stuff for long trips and even potentially making it a mobile base with interiors too.

3) New raids based on this content - Enemy NPC raiding you won't be riding on small boats as a giant horde anymore, instead large entity ships will sail from their 'pirate' islands or such first, and land on your island map, and the unloads and spawns hostile NPC who then raids you legitimately. You'd have to destroy their boats or until they run out of resources (enemy units) and flee with their ships. And they have weapons on the ships to shoot at you if they encounter you in the ocean biomes themselves.