Well there is always the northern passage... Bit of explosives and hey presto, new location lol. Heck if they add-in some blockage-busting explosives some of the other caves might get a bit of an expansion too. The cave where the lame giant ant queen is looks like it should've been bigger. Camp guardian and some of the mines near the southern airport looks like they could be bigger too. There are many possibilities for hidden stuff. Last but not least is vault 21.... That HAS to figure more in the future I think... There has to be a reason 'not at home' sealed it all up...
Yeah, I would at least like to know why Mr. House sealed up 21 like that. Only part is not covered with concrete?
And I agree Big empty seems like its screams Area 51. but thats just a guess.
Long ago when the New Vegas speculation forums was here there were at least 20 area 51 threads at one time or another. I too long ago supported the Aliens in goo tubes idea. No actual combat or meeting with aliens, maybe fine a few holodisks on what was gonig on there.
I remember seeing a mod for a personal hologram unit system, fun mod and you could pick between security gaurd and Vera, I'd like to find something like that.