Every time playing the game has my imagination running wild with all the possibilities.
I'm hoping that at some point Rare would add more islands to the game.
Islands with exploration and even platforming segments, since the movement in the game is pretty awesome. I'm thinking some huge ancient ruins & tombs.
Also Ice-area. Islands changing location constantly, freezing water, navigating through ice, blowing up ice as your ship has become frozen in the ice. And even blowing up ice to create a route somewhere.
And more weather effects, whirlpools, tornadoes, tsunamis, dead wind,
I'm also hoping for a rope, you could swing from your boat, give the rope to your friend below so they can climb up,
Attach your ship to docks, and other ships, tie your rowboat to your ship (Master & Commander style)
Add a spear and you would have a harpoon, imagine latching your sloop onto a megalodon lol.
Or even a simple crafting system,
fire + grog = Molotov
Rope + Spear = Harpoon
Venom + Grog = Poison
etc. The possibilities are there.
Also new "looks" for the ships, as cosmetics. Like different models for different ships (Viking, Cursed, Ancient, Oriental)
One man dingy, basically a raft with a single small sail.