I've been looking for a good pirate video-game but can't find one and DF would be a perfect game to mod into a pirate game.
A crew of a pirate ship is the same as the number of dwarves in a fortress, usually less; you can assign them all the different tasks in a ship the same way you assign fortress tasks; after boarding or when attacking land structures, combat wouldn't need modding, just changing the names of weapons.
I imagine it equivalent to a pretty big embark and a ship that you control from above. You go up z-levels to your sails and that place where a lookout is posted and down z-levels to the sea level, the lower levels of your ship, and underwater.
All around is water that doesn't move so as to not require any processing. Waves would have to be included but be more like chunks of water that move, water should only flow the way it does in DF when it's on the ship.
You would fast travel from procedurally generated port to port and either have your headquarters be the ports of your civ if you're a privateer; or build your own pirate fortress somewhere. In other ports, you would conduct trade like with caravans.
Fast travel would be interrupted by encounters with ships that are far off in the distance(if you have a good Watchdwarf) and you could choose to engage or try to flee; encounters with creatures like krakens, giant sharks, merpeople and so on. These would show up on the map of your embark and you would navigate by assigning commands to the steering wheel or whatever it's called.
Finally, if you're a pirate and not a privateer, your crew would consist of creatures of all walks of life, so long as they are sentient.
So my question to any modders out there is this: how much code would I have to learn to be able to make this myself? All I know is a bit of actionscript and as far as I know, it's impossible to make unless DF turns into open-source but the dream will forever live on either way.
I thought about posting this in suggestions, since piracy is a pretty big part of any world where lawlessness and chaos rule, like in any DF world and adventure mode might yet have it if it's also gonna have caravan escorting. But I think it'd be more interesting to play the pirate ship as a fortress rather than adventurer.