well the gun is rather. thick i should say. so no manufacturer would want to pump out a gun with that much plastic it would need. then on top of that a custom magazine then what shells too ? tanaka or maruzen, if maruzen you then need to have a tank stored in that m16 looking stock or perhaps in the grip. then you gotta wonder overall weight. that and if its maruzen you include the blowback, the tanaka you don't.
if its any interest im having a saiga-12 made. the techs already say how much of a phony pony its gonna be. i have my idea's they have theirs and we are both right on what to do to make it happen. i mentioned this on another site. really your best shot at getting some kind of magazine shotgun that isn't a springer is paying for a tech or DIY get a drum mag with tanaka shotgun shells and do your best to make a DAO-12.