Just because the Medusa digested all those different cartridges doesn't mean it did it "well" or without shortcomings. Personally, I think it was a poorly conceived idea with no point.
This...
There have been multiple "headspace tab," clipless revolvers for rimless cartridges over the years, and there are reasons none of them remain. They're expensive to produce, expensive to repair, and excessively prone to breakage. I've heard lots of guys say these models are "great in theory, but not great in reality," but as a product development engineer myself, I don't agree - the THEORY of relying upon your extractor tab as your primary headspace control is just foolish.
Then expand your thinking a bit to consider the chamber design and you'll realize even more how poor this idea really is. Effectively, it's nothing more than a terribly sloppy chamber. It must be long enough to accommodate the longest of rounds, and large in diameter enough to accommodate the fattest of rounds, which ensures it will not be a suitable fit for the shortest or smallest diameter. So... It's fat enough to chamber 38 Super and long enough to chamber 357mag... What do you think happens when you chamber and fire 380acp? Without pulling the chamber dims, and only looking at the cartridge dims, the 380acp is ~25thou under diameter, and ~6tenths short for chamber... That extractor tab presses it against one side of the chamber, so you can be sure that bullet is going to smash into the inner lip of the chamber throat - how accurate do you expect that to be? Will you not expect split cases after firing since the cartridge is so undersized? That's before you even talk about the fact the barrel will be bored for .357" revolver cartridge bullets, but you'll be shooting .355" pistol bullets in half of these cartridges.
Convertible DA revolvers ARE possible, just depends how fast you need to convert. I have a 357mag/357/44B&D Redhawk with two cylinders assemblies. It takes me about 5min to pull the grips, pull the trigger guard, and replace the cylinder currently, but it's very nice to be able to convert back to 38spcl for plinking instead of running full house 357/44 loads. I'm currently working on a push button crane release on some spare trigger guards, but have other projects on my bench taking more of my time. Worst case, a retaining screw design is super simple, although my ultimate goal is to be tool-less for conversion. If I so desired, I could either moon clip my 38/357 cylinder and ream the chamers to accept 9mm, or better still, pick up a 3rd cylinder assembly. I've thought strongly about making a moonclipped 357Sig cylinder for this revolver, and having dies made to use .357" bullets, but I suppose I never will, since it uses just as much or more powder to load for the 357sig as it does for 38spcl, which I already have, AND Spcl brass is cheaper and more readily available, not to mention, no moon clips.
I've spoken with Gary Reeder about doing a convertible GP100 as well, one cylinder in 256Win mag, the other in his 255 Banshee. He doesn't favor the 256wm for the obvious historical problems, but I'm preferring to have both to let me use simple 357mag brass instead of being wholly reliant upon Hornet brass. This will have the same downside as my current Redhawk, requiring substantial disassembly to change between cylinders, but in reality, that doesn't pose much of an actual problem - I rarely shoot both in the same session, and it goes relatively quick to change anyway.
