I see only one problem with patching the barrel and putting Briley tubes in it...somewhere down the road someone might take the Brileys out and fire the gun with high pressure 20 ga. ammo and it could blow up in their face.
I still think the lamp is a better choice and would see more use...the two hammer gun lamps I saw were mounted up right on a wooden plaque, the barrels were chopped about 5 or 6 inches up from the breach and the hidden electrical cord ran through the gun.
The guy had two of them for sale....I wish now I had bought one or both of them.