Pirates of the Padomaic
This chapter would focus on the northern ocean and seas, including the islands. The islands opened up would include Sheogorad region of Vvardenfell. The theme would be seafaring but would also have influences from all coastal seafaring races.
The Main Quest:
The focus would be on a story centered around Haknir Deathbrand, the legendary and infamous pirate king of the northern seas. Perhaps the player could earn the respect or ire of this pirate king. Haknir was a ghost by the time TES V comes around and had been dead for centuries. I don't think the lore specifies what era he lived in so he could be alive during the 2nd Era.
Locations:
The islands of Sheogorad
Other islands that are not shown on the current maps of Tamriel.
Dungeons:
Each island would have its own unique dungeon.
Housing:
Notable House: A Pirate Ship in the middle of the water somewhere, not docked in a "hidden cove."
Notable House: A "pirate island" with a cave and other hiding places to hide one's loot.
Furnishings:
More maritime furnishings
Corals, barnacle encrusted rocks, sea creatures, seafood, flags, odds and ends associated with pirates, animated canons
Valuable treasures from each race of Tamriel
Non-combat Pets:
Pinnipeds
Mount:
large walrus-type
A dinghy - perhaps the code could be adapted so that this could only be mounted while in water just like land mounts can only be mounted on land. I feel it would be cool if we could ride in a boat instead of swim around in the water.
Costumes:
A "pirate costume" each for men, elves, and beast folk.