To answer the origional question I think what you describe has been invented some time ago. Its called a Ruger 10/22.

As I sit here doing some quick math I have concluded that my trusty Ruger 10/22 has:

(1.)Had over 10,000 rds put through it.
(2.)Has never needed a part replaced
(3.)Has stocked my freezer with countless tasty critters over the years.

It it reliable, reasonably accurate,easy to use and has only jammed a select handful of times usually due to being dirty or frozen while hunting rabbit at -50 deg cel. It dosen't break down like some models but I have yet to have a real reason that I would need it to. If a 10/22 is too bulky or heavy for you then you most likely don't belong in the woods to start with.

Spare Parts and ammo are virtually everywhere you can imagine and it is a gun that anyone can afford to own and shoot often as to build up a high level of skill. I can buy about 500 rounds of ammo for the same cost as about 10 rounds for my .338 L.

Its as close to the perfect survival gun as anything I can imagine. Everyone should have one.

Oh, and by the way. I, as some of you spend a lot of time hunting in dangerous game territory. IMHO, ANY gun you think is the final answer for self SD against a charging griz is nothing more than an expensive false sense of security. I have heard tell of people point blanking these monsters with .30-06 several times and still ending up geting mauled. I am not saying that a large bullet won't help, but in the long run the best defense you have against dangerous game is never to put yourself in its path. Know and respect your foe, and give it its space. Buying a survival gun out of fear of getting killed may be a waste of money if thats your biggest concern. Rutting Moose make plenty of noise so your best bet is to stay the hell out of his way rather than humping an artillery barrel on your back every time you hit the woods.

Just my thoughts