Well that flash hider isn't going to do much where its mounted. As for the bipod on a shotgun, i'll pass but hey if thats what you want then go for it.
Edit: i'd give up bipod for a bayonet. I think there more fitting on shotgun, as most shotguns are used for close encounters where as rifle would be used for longer distance. Then again historically the rifle has been the bayonet weapon. We have the pistol bayonet thing so why not a shotgun one? Heck put one on each type of weapon and you won't have to worry about not having one when ya need it.