A fair point, but come to think about it, even if the Courier was a good person, the Tunnelers would've invaded the Mojave and whoever was left in charge had to deal with the onslaught anyway.
...That does sound a bit like DUST.
Also, though it might be a little contrived, have the remnants of the Ghost People go out and explore the Mojave, dragging in any unfortunate victim back to the Sierra Madre.
I know it might be much, but I wanted to throw around some ideas. Maybe I could throw around something like this:
Least bleak:
-
NCR, optimal (or mostly) path -
Independence/Wild w/ Securitron army -
Mr. House, good Karma
Not so bleak:
-
NCR, neutral or a less optimal path -
Mr. House, neutral Karma -
Independence/Wild Card w/o Securitron army (maybe? Could also apply to most bleak)
Most bleak:
-
Caesar's Legion -
Mr. House, evil Karma -
Independence/Wild Card w/ evil Karma