You could make amnesia part of the story of how he got to New Vegas, maybe like the airship crash in Tactics except where he forgets everything and starts a new life in the Mojave? Just an idea. Haha. :]
Good idea. Like he decides that DC's had enough of him, so he travels across the continent helping people here and there until he finally reaches New Vegas. He becomes the Courier until he's captured and shot by Benny (which gives him amnesia, which helps explain why he's going to have to relearn how to shoot a gun, use a pipboy, etc.)
Eh, it's not very original. I hope it's optional to relearn everything, so I can just walk out the door and begin the new adventure.
EDIT: I concur, francisthemutant. If the Wasteland of DC taught my character anything, it's don't blindly trust anyone, anywhere.