I think a 45colt version of the 22-4 would be the ideal "Mountain Gun". No adjustable sights to monkey around with, nice tapered barrel with a rounded front sight slides in and out of a holster slicker n' snot on a doorknob, and the square-butt N-frame grip with the "Thunder Ranch" stocks feels perfect to me. I can't warm up to the Ahrend square to round conversions, and a round butt only feels right to me on an L-frame snubbie.
If S&W came out with a 45colt version of the 22-4, or the 58, I'd buy one immediately. For that matter, if they came out with both, I'd buy one of each. I wonder how difficult it is for them to set up for something like this. 45colt MG cylinder in a 22-4 frame, with a overbored 22-4 barrel with less meat sticking into the frame window. That doesn't seem to hard, especially since they already bore out the same barrel length for the Mountain Gun.
If they were going to do it right, they could use the same heat-treating as they use on the 29. Wishful thinking, but it would be nice so you could reload slightly hotter loads if you wanted. I'm sure the legal staff would nix this idea, but this is the wish list section, right.