I would love to see the WBOS sneak a nuke into the NCR Capital. Just one, I think thats all it would take to thrown the NCR into a chaotic civil war (as if there's some other kind)
That just wouldn't happen. I don't think their feud runs that deep that they would resort to such drastic measures, like killing 100s of thousands or maybe even around a million people. There are some zealots in the Brotherhood, yes, but I don't think that would happen. If it did, I'd be annoyed.
For the original thing, no, that's a part of Van Buren I never want realized. We don't need re-nuking to make the game feel more apocalyptic, just uprisings in the current major governments causing instability. That's the best we can hope for with the "must move forward" doctrine at Bethesda.