A barrel-extending muzzle device mounting system?

[Pericles]

A curious idea came to me this morning and I'm wondering if anyone here has ever seen or contemplated such a thing. Here's my problem: I was thinking about welding a suppressor to my barrel so that its total length would come out to just over 16 inches. That way I wouldn't have to jump through the SBR hoops (another $200 tax stamp, can't take my SBR'd receiver across state lines without ATF approval, or to a state that doesn't allow them, etc.).

So, while I was wondering about the practicality of doing such a thing to my poor barrel, I started thinking: Is there a better way to achieve the same goal? That is, is there another way to extend the legal length of the barrel, besides welding on the can?

My first thought was, OK, why not weld on a simple steel tube so that it protrudes four or five inches beyond the threaded end of the barrel, thus making its legal length just over 16 inches. Then I would simply insert the suppressor into the tube and screw it on to the barrel. I could even drill holes in the tube to make it lighter and easier to clean.

Has anyone ever heard of something like this?

A more advanced conception also occurred to me. Imagine a 12" barrel that sharply flanges out to, say, 2" in diameter at its end. From this muzzle face extend three 4"-long integral steel pins that are arranged in a triangle. This brings the barrel to the legal overall length. Then you could buy a variety of compatible muzzle devices (flash hiders, brakes, suppressors, etc) that slide snugly over these pins and lock in place by means of some simple screw-type system that interfaces with ridges or notches in the pins. (Hopefully the pins would not interfere too much with the design & operation of the devices. I don't think they would pose too much of a problem, but I'm not an expert here.)

So that's my weird muzzle contraption idea for today. Any thoughts? Am I insane or totally misguided?

(P.S. Here's another strange idea along the same lines: What if you welded a steel bayonet underneath your barrel? Would that extend its legal length?)