A city in the water that was constructed before the great war with its own problems

Bioshock but I have a feeling thats what you were getting at.

Couldnt call it Atlantis because it is described as being in the Atlantic and the Mohave wasteland is a longways away from the Atlantic ocean.

I wouldnt mind getting a look at Area 2 which is where those big howlizters came from that the Boomers have at Nellis. But I doubt that would even be done in even a DLC considering they are gun nuts they most likely picked that place clean.