This is actually a brilliant idea, specially if they were to do it via DLC before New Vegas comes out. Get everyone who hasn't played or just doesn't remember fully the happenings of Fallout 1-2, tactics even. They are nigh impossible to find. I would Download them the day they came out on Xbox live.
As I pointed out. None of the groups which could do an Xbox LIVE release can or will.
Interplay only holds the rights to distribute the originals unmodified on the PC.
Bethesda holds the rest of the rights, but have no interest in recoding and rereleasing somebody elses work*. (And they'll need extensive recoding to work on the Xbox)
*Also why they didn't finish Van Buren.
As for being impossible to find?
The Trilogy (1,2 and Tactics) can still be found in shops.
Good Old Games has them. http://www.gog.com/en/search/sort/search/fallout
They are availiable on Steam.
I think a couple of other online retailers have them too.