Jeff Cooper's "Super 9" was .223 brass, cut to .38 Super length, and used in a modified commander. The thicker rifle brass allowed higher pressures. As I recall, the extractor had to be modified to work, but I think he was using the standard .38 super extractor when he found it needed modification.
The Coonan .357 is a neat gun, and the mags do work. However, like the Desert Eagle mags, they have openings so, some kind of shrouded magwell would be needed to keep dirt out. And, they aren't exactly common.
Making a rimmed round work in a magazine is not as difficult as everyone seems to think it is, witness the millions of .22RF autopistols. The trouble with autopistols in .357 is the length of the round having to fit in the grip, and the average size of the human hand.
One could easily design and make a single stack rifle magazine to handle the .357 magnum, the main drawbacks are a) either fitting it to an existing rifle platform (M1 carbine/AR/Mini 14, etc), or b) making a new rifle just for it. It could be done, but it won't be done by any maker, unless they believe there is a market sufficient to justify the expense. And, frankly, there isn't.
People wanting a .357 carbine are generally happy enough with lever guns. Maybe some dedicated hobbyist with his own machine shop could build one, but in these times, I doubt he could sell enough to justify making it a business.
Wish I was wrong, though.
