I did some quick cad drawings to determine what might work. It would appear that if the ratchet diameter could be reduced slightly you could get 5 45 colt chambers with a bore of .481 and a rim diameter of .512 in a cylinder with a diameter of 1.641 (which I would assume is close to an L-frame cylinder, but I only have K and N frames on hand at the moment). If the ratchet could be reduced further (below .48" diameter) the cylinder diameter could be even less. With a 1.641 diam cylinder, it appears you could get 6 41mag rounds, 7 40s&w rounds, 7 357mag or 38special rounds, and 8 327 fed mag rounds in the cylinder based on the standard case diameters plus a modest overage. I checked the listed case rims when applicable, and they all seem to work, too. I believe the cylinder stop notches work, as well. I don't know how much meat you need at the minimum locations between cylinders and at the outside of cylinder to outside or bore, but the 45acp and 45colt chambers meet or exceed the amount on my model 25, and 22-4. The 40s&w seems to have the least amount of material, so perhaps it would need to be a 6 round (especially if it were 10mm/40s&w).
I think if S&W would develop a frame around a cylinder similar to this, along with a frame that allowed for the required material where the barrel threads in, they could use it for quite a few arrangements. Two lines could be developed. One would be a fixed-sight version with barrel lengths in 2-1/2", 3", 4", and 5". Two barrel options could be offered. One tapered like the 22-4 or mountain gun, and one heavy like the 58. I'd like to see the 4" and 5' in square-butt, ideally, with round butt 2-1/2" and 3" models.
The other line could be adjustable sights, with similar barrel length and butt arrangements except that 6" and 8-3/8" would be offered as well. 2-1/2" thru 4" models could be offered with full underlug, and 4" thru 6" could be offered in tapered barrel if desired.
They could call the frame size an V-frame (for versatile), and maybe even start a new model naming convention starting with 7, and ending with the caliber, such as a model 738 would be a 38 caliber, and a 741 would be a 41mag. Stainless could be designated by an S at the end of the model number, to reduce model number confusion.
I know this is a lot of wishful thinking, but I was bored at lunch today and wondered if such a thing was possible. I know I have oversimplified things, and retooling and parts would be costly, but a single frame size that was a mix between K/L frame grip size and L frame cylinder size, with adjustments made at questionable locations like the forcing cone area (ala 696) in order to prevent foreseeable issues. They would need to apply some ingenuity to the yoke arrangement to provide more meat below the bore opening in the frame, but with modern materials this should be possible with a redesigned frame. If they could come up with an internal ratchet that rotated the cylinder with similar to their polymer revolver arrangement they could reduce the ratchet diameter and juggle the dimensions between chambers and the center pin to bore dimension until it was opitmum for the broadest range of cartridges. Obviously, this would also affect the yoke, but I think they are up to the challenge. It all seems possible, but not probable.
I guess I need to get a cnc machine and find a friendly forge/foundry in the local area.
Personally, If it were feasible, I'd take a 3" Round butt 10mm/.40 S&W K Frame, too! 
:grin:
