I forgot another goldmine of folding guns that would make a halfway good survival system. Kel-Tec. Guns like the SU16C, SU16B, and SU16A. They all fire .223 rounds and use standard NATO magazines. This makes them a bit MORE than a mere survival rifle. They're all pretty similar, different barrel lengths and otherminor differences, and they all fold up. At least on carries spare mags in the stock. This is the B version.
And then there is the Kel Tec Sub2000:
which fires pistol caliber in 9mm or .40 cal. You specify the magazine type you want when you buy it. Also closer to a regular carbine with that type of caliber.
Now THAT is intriguing, if they come out with one that fires 1911 .45 mags.
Kel-Tec impresses me more and more. All reviews I've seen of Kel-Tec products go something like: "The gun was so cheap I figured that meant it would shoot bad and unreliably, but I was pleasantly surprised. I wouldn't enter any shooting contests with it, but I'd trust my life to it."
The styling on Kel-Tec is very modern. I'm more of a classicist. If you had a Marlin Camps Carbine and a Kel-Tec SUB2000 out in 'public' both firing the same round in the same numbers, the Kel-Tec is going to scare the hoplophobes, while the Marlin, with it's walnut stock, the hoplophobes might be less panisky because it LOOKS like a classic hunting rifle. Sort of the same reason to put your Bug Out Bag in a school backpack rather than a Tactical Black Stack-Up vest that LOOKS like something a ATF agent would wear to take down a cult compound. No one looks twice when you carry around a school backpack, they think you are a mall ninja when you have the tactical rig on.
I DO have a carbine or two on my wish list...