I don't know about lore but a fun game mode could be a survival mode on a skeleton fort similar to the Call of Duty Zombie game mode.
Players spawns on the dock with a sword, kill skeletons for points to spend on unlocking the higher levels of the fort and weapons.
Each round gets progressively harder and every couple of rounds a captain or skeleton Lord appears, maybe even a fleet that circles the island and shoots cannons at players.
Would you play it? I know I would. I know it's not the intentions Rare had for the game and I wouldn't expect them to make such a mode but I think it would be very fun and could bring a few more players in.
Maybe it could be a new kind of order of souls voyage so that it stays in adventure and keeps the threats of other players
