Wanted to know what people thought of this idea? Rather then do a Shivering Isle type DLC where we go to another land, What if we went beneath the very land of Skyrim itself!?

Think about what if all the Dwemer ruins near to the surface which we explore, loot and are Falmer inhabited are merely the city gates which originally led to a massive city beneath the earth.

Like http://www.superbwallpapers.com/fantasy/underground-city-2868/ or http://theroundtablet.com/wp-content/uploads/2011/09/punished-city.jpg but Dwemer. I'm not talking about ruins either, this would be a city that has been cut off since the Dwemer disapeared and has been taken care of by its mechanical custodians. The DLC would start with rumors of the city being found and settlers moving down their. Their would be several small settlements and a few trade outposts.

It would be like the Gold Rush were all different people from Skyrim moving down their hoping to make there fortunes from the dwemer ruins but something happens! One of the settlements is destroyed but no one knows by who? Turns out the ancient mechanical army has been triggered, the machines not realising that the dwemer are gone simply act as if the city were under seige/invasion by an enemy army and lock/destroy the tunnel to the surface! Now the dragonborn must save everyone trapped in the city by finding a way to deactivate the army. Mayby you find out by the end of the story line that it was tyhe Falmer who activated them wanting to have the newly discovered city to themselves perhaps as the a new homeland.

I am hoping that a future DLC will allow us to time travel in a certain underground area that already matches your description. I can only imagine what that place looked like in the past. Think it would be really cool.
If you haven't been to the area I am describing yet, you should check it out. It's part of the main quest.