Wganz, the 32-20 'parent' I suggest already has a rim too, and does not require the somewhat troublesome neck reforming, so I dont think the 30-357 would be easier to do overall; plus the 30C dieset is likely found reasonably priced, if not cheap on a gunshow table. I havent been all that fond of the bottleneck on the 32-20 and havent I heard that carbide dies are available for the 30C? Carbide does make the resizing go ever so much quicker and easier (and a bunch of us just like mostly straight cases anyway).
The 32-20, .310 Cadet, and higher performance 30C have all proven themselves as viable cartridges from cast bullet through jacketed so the 'size' is good, and with the faster twist of the typical 30cal. barrel should be good for longer/heavier bullets of both persuasions for sub-sonic, schuetzen, small game, plinkin', etc. I know at least a couple of guys have campaigned the 32-20 quick twist for schuetzen matches. No reason it cant be done with a plain base 30cal. cast bullet.
Now if the case I suggest doesnt have enough powder capacity for one, that 30-357 could very well be the next step up, and I have liked that cartridge since hearing about it some years back.
This notion of mine is one of those 'what if' concepts.