You guys have a bunch of great ideas. There seems to be a decent sized interest in a gun like this. I believe the Ruger LCR has the most narrow cylinder at 1.28 inches, but as stated in a previous post someone measured thier 5-shot 32 S&W long at 1 1/16. That comes out to 1.06 in width across, and a J-frame is about 1.34 inches I believe.
Now factor in a shorter cylinder, which will make the overall gun length less, especially if you keep the barrel at 2" or less. And with just using the steel/aluminum format (maybe even polymer nowadays), you should come out with a gun that would be 12 ozs at the most. So overall the width would be decreased, the weight, and the length. I would also imagine the height would be a hair smaller as well.
And chambered in 32 H&R mag with a 100 grain bullet hitting 900 FPS you would have a very good SD round. More energy than a .380 auto round, and would probably beat out most standard pressure .38 rounds as well. And for the range or those who couldn't handle the recoil, you could fire 32 Long, which would still be effective for SD with a 100 grain wadcutter round.