The introduction could have been easily mended by spending more time Pre-War and having a Fallout 3 style "Two weeks later" timeskip after talking to the Vault-Tec representative. Then, in the late afternoon whilst watching TV (You could have the Mister Handy advertisement from Fallout 1 here) with your spouse, the TV is interrupted by breaking news of the west coast having been annihilated by the Chinese. You rush off to the Vault in a sequence similar to the current one, but there's no nuclear explosion as you go down the lift, instead you just hear gunfire as the security forces fire off into the crowd outside the Vault. As you're suiting up in your jumpsuits, you hear booming sounds from above the ground, the vault quakes and the lights flicker, everyone looks around nervously but the Vault-Tec staff nervously reassure you that everyone is safe and tell you not to think about it. But that wouldn't be epic enough for Bethesda's audience.