Use the Tactics weapon set. Limiting Fallout to "No real guns" is stupid in my opinion. It's not a completely different universe, it diverged shortly after WWII. It's the world that would have resulted had MacArthur nuked the Chinese in Korea, like he wanted to. So WWII weapons and maybe AK-47s are completely doable. And lest ye think this was just Tactics, the first two Fallouts had Desert Eagles in them. In the flavor text, it attributes their popularity to "an interest in 20th century movies."(Snatch?) That doesn't exactly sound like an entirely different universe. It irks me that Fallout 3 insisted it was a different universe, something previous games had never done. Examples? Tommyguns, a Hummer, and the Preacher comics.
More ammo starvation. The original Fallouts were guilty of this too. It's a wasteland, yet I find hundreds of shells lying around?
The Steel Scourge, the evil option from the end of Tactics. The Brotherhood of Steel becomes a xenophobic fascist Inquisition, killing anything the least bit mutated. The Enclave are played out as bad guys, it would be a nice twist that the knights who save your ass in the first game are now the biggest threat to NCR and the population in general. On the West Coast, we've no idea what they've been doing for over a century, other than that they wanted Vertibird plans.