You won't get it to change for 3-Gun. The shotgun market is much too well established. It would be a bigger bust than the 9 MM Federal, or the .45 GAP. The brass itself is much too thin to reliably headspace on. Not only that, but it is not reliable in height now because it doesn't need to be.
It would require an entire new line of ammunition and guns to go along with it. The market would be too limited, and the guns and ammo would be cost prohibitive. Trying to get a new cartridge on the market is a financially risky proposition. Look at the Remington SAUM's, and several of the other short, fat wonder cartridges. Ammo and brass is hard to find, and the guns for them are always heavily discounted because no one wants them.