Have been paying a bit attention to the talks of new big threats (like Kraken), and seen many talk about Davy Jones. As many in these discussions have pointed out, there already is a ghost ship; the one you end up on when dead.
Why not just turn this into Davy Jones' ship completly? Change the captain to Davy Jones, give the ship functional cannons and man some of them with skeletons.
Just like Kraken, the ship of the dead morphs into "reality" at random occurances, and opens fire on whatever ship might be close.
And to make it extra fun; Dead players join the crew of Davy Jones, giving them access to the cannons so they can blast away at other players ships. Might be a good way to kill some time while being dead, if you happen to die at a time when the Flying Dutchman is engaged in combat.
Just like Kraken seems to appear when you have lots of treasure, Davy Jones would have bigger chance to appear if you and your crew have sunk a lot of other ships, and you will have to pay your "debt". This would also bring on an extra element to the PvP, as if you just sink other ships while doing quests, you don't want to meet Davy Jones, or maybe your crew want to meet him and start hunting.
Just a thought =)
