I'm totally happy with that; I don't look at visual destruction as much as moral destruction. You know, no black and white, but all black or at least dark gray. All factions are bad, bad people all over the damn place, few good people willing to join the cause of helping humanity... that sort of crap.
I don't mind NCR restoring train tracks and running trains with goods and soldiers over the few states they have. Besides, we all seem to be forgetting there's practically no oil. Without oil, there's pretty much no civilization, unless a few masterminds collect and think of new fossils. So to be honest, even if the NCR keeps on fighting and reaches DC, Canada and Mexico, kills raiders and mutants, they still haven't got ships (or only a few) or planes (only short distance ones) to advance. Hell, we probably wouldn't see cars. Only brahmin.
Come on. Have you seen what the Republic controls, anyway? If we make games with little time in between them and set them in outer areas (such as my own idea is set to the North, near the Canadian border and even reaches out for a part of Canada, just above the Fallout 2 map) where there's still no law (or perhaps instead of Shady Sands, an equivalent of Khans prospered). Hell, we could even see a new Brotherhood-type group, except the fact that it wouldn't be so xenophobic and would come out there to kick more ass in Power Armor. Maybe they're set to kill everyone out there (Enclave), or maybe they're helping everyone instead (but see NCR as a bad choice).
Lots of ideas. Millions. I made this up in 5 minutes and it sucks, let's brainstorm for 5 months and I guarantee you, it's not going to suck as much.