Uhm. I am sorry to say this ... but that is pretty much what they did ... sure FEV, VATS and Vaults exist in the Fallout universe. But that doesn't mean that what Fallout 3 has makes really sense. Like the Encalve, the BoS and SuperMutant research beeing all relocated to a completely different coast thousands of miles away from the actually source... for ... what reason exactly? The things we talk about exist in Fallout. But that is pretty much all of it. Thats where the SM infestation in DC pretty much ends. They had the virus, a vault and that's it! So they are there and kill everyone. The truth is they are savage mutants without any reason to be there. They are only there as target practise. Nothing more. Nothing less. I have my own theory why Bethesda decided to add in Super Mutants and also Enclave and BoS to F3. Because otherweise you would have a very very hard time to actually reckognize Fallout 3 actually as a Fallout game and not Oblivion with gunz. The fear from Bethesda, someone could get the idea that it's not a true Sequel! - And they also never got tired of reminding people that this is what they wanted to do. But hey, don't worry it got Supermutants and Enclave and even BoS and a wasteland surounding it and a hell lot of violence! With nukes! Lots of nukes! So it's a Fallout game! That is exactly what those might think that never really played the previous games.