I think it's an excellent idea. Tweak the interface a little and make it more amenable to shorter burts of play a la the DS remakes of the FInal Fantasy games and it'd definitely be a goer.
The fallout gams are long games, whereas Hendheld consoles excel at short gaming sessions. That, and the interface not being easily transferable and the lack of a need for it makes this a huge no.
There are literally hundreds of JRPGs on the DS, games that expect a 40 hour+ commitment, so to say that handhelds only do "dip in, dip out"-style games simply isn't true. The last Dragon Quest game wan't even released on a home console, but was on the DS instead.
edit: lol at the idea that decade-old PC games are too much for the hardware to handle.