Ruger Super Redhawk (without the extra metal up front) fitted with a set of Dan Wesson Barrels, 4", 6" 8" and maybe 10" with lightweight shrouds for the longer lengths.
44 Magnum, 45 Colt, 45 ACP, 454 Casull and .357 Magnum.
If I am limited to only one gun, I would have 5 cylinders in the above calibers, cylinders and barrels to match, which can be interchanged all on the same frame.
The 45 ACP cylinder would be a true 45 ACP, not just a 45 Colt cut for moon clips, but shortened (and the barrel would, of course, extend into the frame opening) to the freebore "jump" to the forcing cone and rifling would be minimized.
I would have thrown a 480 Ruger into the mix, too, but I wold rather have that chambering in a 5-shot. Of course, none of these are really combat revolvers, so having all in 5-shots would not be that big a drawback for me. (And, since the .357 Mag Redhawk is reputed to be the strongest .357 revolver ever made, a SRH 5-shot .357 would be far ans away a head-turner, especially if it took .357 Maximum. My juices are cooking NOW!)
Extra shrouds with picatinny rails on those long enough to allow clearing the ejector rod.
One would have to be extra-careful to ensure the barrel calibers match the cylinder chamberings.
Price tag for all the above? In my DREAMS! (Which is, after all, the point of this thread, right?)
Lost Sheep