Blizzard should give it the "Blackrock Spire treatment": uninstance part of the cave system, add a portal to the Detention Block dungeon, another for the Shadowforge city Dungeon. Then, seize the opportunity to put a third entrance (not portal) that leads to an uninstanced version of the city.
It would also be the perfect opportunity to revamp/update those dungeons. Either do what they did with Blackfathom Deeps, in which they just put new mobs/story for the low-level version of the dungeon, or like Scarlet Monastery, in which we get both low-level and max-level/heroic versions.