I was bored. So I wrote this. Feel free to bash it or compliment it or whatever. Assuming that "The Dark Below" is a real trademark, this is what I would do with the expansion.
General intro to expansion
Following the defeat of Garrosh Hellscream, the world is still healing after the cataclysm. In the aftermath of the siege of Orgrimmar, an ancient Titan artifact is discovered in Pandaria. This artifact has the power to bend matter and create life itself. It also provides the means to open doorways, doorways to places previously unreachable by the beings of Azeroth. The Old Gods, having failed in their bid to break free of their prisons using Deathwing as their pawn, resort to Plan B, gaining control of this lost artifact and using it as a means of finishing the work that they started. They call upon their final ace in the hole, Queen Azshara. As both the Horde and Alliance face a new threat from the sea, tensions continue to rise as both factions aim to capture the rumored titan artifact for themselves.
..-Azshara under the influence of N'zoth is leading a full scale invasion of the South Seas.
..-The Zandalar Tribe continues to unite the remaining troll nations from their capital, under the leadership of the mysterious prophet Zul.
..-Ruined sea faring factions are recovering from the cataclysm.
..-Draenei come to the forefront of Lore for the Alliance as Valen sees the Titan Artifact as a means of striking back at the Legion on Argus.
..-Trolls come to the forefront for the Horde as Vol'Jin strives to stop the prophet Zul from taking over the South Seas.
..-Northrend and Outland lore progresses.
...New Map Region: The South Seas
.....-Azjol Nerub (94-95) - The cataclysm opened fissures into the vast underground kingdom of the Nerubians. Their kingdom was dessicrated by Arthas and the scorge but after the fall of the Lich King those few living Nerubians have slowly begun to repopulate the ancient kingdom. This zone is entirely underground and holds direct connections to Dragonblight, the Broken Isles and Deepholm.
.....-The Maelstrom (94-95) - The center of the Cataclysm, Deathwing's bones line the reefs of the sea floor but the elementals are still in a state of unrest in this region. The Earthen Ring has set up shop on the spires overlooking the vortex and are locked in constant combat with the elementals. Large portions of this zone take place deep below the ocean.
.....-The Broken Isles (94-95) - This is a zone like Vash'jir. Most of it is under water. And it is the home of the eventual final raid through the city of Nazjasar. The Tomb of Sargaras is also here.
.....-Zandalar (93-94) - Troll capital island.
.....-Tel Abim (92-93) - Island zone under Naga attack.
.....-Plunder Isle (91-92) - Home of the bloodsail pirates. Other dangers lurk here too, but bloodsail admirals will finally have something to use that rep for.
.....-The Lost Isles (90-91) - The Old Goblin Starting zone, Phased for level 90. Goblins are looking for Kejamite, the Alliance are looking for a new foothold off the coast of Azshara. (Zone Favors Horde)
.....-Gilneas (90-91) - The Alliance has moved in force to push the Forsaken out of Gilneas. (Note this phase does not activate until level 90. Silverpine quests into Gilneas still function for the Horde.) The Alliance are using Gilneas as both a port into the Northern Eastern Kingdoms, and also as a close connection to Kul Tiras. (Zone Favors Alliance)
.....-The Open Ocean (90-95) Deep nearly bottomless ocean that connects all of the islands of the South Seas. This is the transit area. Flying Mounts work here. As well as aquatic mounts. There are ancient mysteries sunken in the deep. No one can simply dive down there to find ancient treasure as it seems the ocean floor is always changing. Secrets and treasure will be added deep into the ocean every patch. But it's up to the server population to find them.
.....-Kul Tiras: Alliance Capital. Jaina Proudmore has returned home and commands here along with Genn Greymane. Boats traveling to Gilneas and Stormwind.
.....-Undermine: Horde Capital. Galywix returns to Kezan. The great Goblin capital was all but wiped out after the Cataclysm. The original Goblin starting Zone is still here but totally destroyed. The Underground capital is occupied by the Horde as a port to the South seas. With connections to the Lost Isles and Bildgewater Port.
-Key Expansion Features:
...-Level Cap increased to 95.
...-One Massive World. All of Azeroth is put together and is no longer separated by loading screens. Dreanei and Blood Elf starting zones are updated to a post cataclysm state and fully connected to the world, allowing flying mounts better continuity with the world. Northrend and Pandaria are also connected to the world. Outland remains in a different dimension.
...-Outland and Northrend updated to post Cata lore. Level ranges of Zones changed to add variety and choice to the leveling experience so it's not such a brick wall for new characters. New logical leveling paths have been opened so that former end game zones see more traffic. The druids in Silithis have opened a portal to Nagrand in Cenarian Hold.
....-New Level Ranges:
Hellfire (58-62), Zangarmarsh (62-64), Blades Edge (64-67), Netherstorm (67-69),
Nagrand (58-63), Terokkar (63-66), Shadowmoon Valley (66-69), Quel'danas (69-70),
Howling Fjord (69-73), Grizzly Hills (73-76), Zul Drak (76-78), Storm Peaks (78-80),
Borean Tundra (69-72), Dragonblight (72-76), Scholozar Basin (76-78), Icecrown (78-80),
...-South Seas: The Islands of the South Seas are all connected to underwater Zones like Vash'jir. You can fly from island to island. Fatigue zones keep you out of places you shouldn't be.
...-World Bosses on the open sea. Rare Spawn world bosses that update their loot each raid tier exist out in the vast ocean. It's not as simple as parking a level 1 alt at their spawn point anymore.
...-Guild Gunships- Guilds can purchase boats and engage in sea combat. Boats can be boarded and attacked by the opposite faction. Guilds can upgrade their boat with bruisers, guns and other awesome gimmicks. (For a Price). Guild ships can only travel through the massive Open Ocean zone. The ability to purchase a ship is tied directly to the guild perks system, new perks include portals to the new zones directly from your guild ship, your own flight master on your ship. Eventually guilds will be able to purchase airships that can travel anywhere in Azeroth. The guild leader can assign piloting authority to any guild rank and a patrol course can be plotted anywhere in the Open Ocean.
...-Guild Diplomacy- Level 30 guilds can create alliances with other guilds on your realm and faction, allowing you to better communicate, share resources. Declaring war with a guild of the opposite faction will flag members of that guild with a special aura and provide bonus guild experience and rep for killing members of that guild. Of course war goes both ways.
...-More Archaeology options.
5 Outdoor PVP Zones - Each zone is on an 5 hour timer and each battle is offset by 1 hour.
...-Tol Barad updated to level 95. New dailies put in place and new rewards added. Holding Tol'Barad will produce a benefit for the entire South Seas region when it is held.
...-Wintergrasp updated to level 95. New quests added to the zone. Holding Wintergrasp buffs the South Seas and Northrend and stacks with Tol Barad.
...-The Ruins of Anj-Quiraj PvP Zone. South of Silithis lies the ancient ruins of Anj'Quiraj. Another outdoor PVP zone with level 95 daily quests, rewards. The faction that controls AQ, will provide a buff to Kalimdor and the South Seas.
...-Alterac Mountains PVP Zone. Like AQ, the Alterac Mountains now also becomes an outdoor PVP zone. With new rewards and Dailies and a Buff for the Eastern Kingdoms and the South Seas.
...-Southern Kasarang Wilds PVP zone updated to level 95. New PvP objectives have been added to the region. Buffs Pandaria and the South Seas.
Potential 25% buff to reputation, experience, justice, and honor gain in the south seas region if a single faction controls all 5 zones. In addition, every zone controlled improves the spawn chance of a world boss within the Open Ocean.
Weekly Classic Raid Challenges - Flex raid technology allows nostalgia trips to classic raid content. Guilds can make pre-made groups for classic raids. By selecting the Flex raid difficulty level, premade groups can scale the raid to level 95 to experience the raid as it was originally designed. These groups can earn Valor, scaled up classic gear (Including Legendary Items) and reputation with the Timewalkers, a mysterious new faction that is very interested in the past exploits of the heroes of Azeroth. Each week the Timewalkers will have a weekly quest to complete a classic raid. Completion of this quest will yield guaranteed loot for everyone completing the quest. Fear not, those who are wanting to solo old content at the original level it was designed for can leave the raid difficulty on normal and two shot Ragnaros if they want.
Classic Challenge Modes - With the launch of the new expansion, challenge modes will be added for all of the new dungeons. Existing Pandaria challenge modes will scale up to level 95. Each time a Gold ranking is achieved in a dungeon, a new classic dungeon challenge mode will unlock. In addition, the completion of Gold in a classic challenge mode will unlock a level 95 version of the dungeon into the normal dungeon finder. Players may queue for either a Deep Below dungeon or a Classic Dungeon. Mounts, Tabards, Profession Recipes, and reputations can be your reward for completing this classic content. The Timewalkers will also have daily quests to complete classic Dungeons. There are rumors that when every dungeon has been completed something Legendary will happen.
Hearthstone - Access to the hearthstone CCG from within WoW. There are hearthstone tables scattered throughout Azeroth and hearthstone masters to challenge. Build your deck and challenge other players or to combat. Rewards include exclusive Hearthstone cards only available through WoW, battle pets, mounts and cosmetic rewards.
Pet Battles Mobile - Take pet battles on the road on your iOS or Android device. Battle other players from anywhere.
That's it for now. As I said, I was bored.