I just got an upper from Spike's Tactical and they will remove the Bayo lug for you (i forgot to ask) for like $10 i think...
Also, they will pin a stock for 10-15... the local gun shop told me to pin and epoxy the pin (just some over it)... so it is clearly not adjustable any longer, but could be adjusted by an armorer with the right tools, or a hack like me with a dremmel, lots of time and low standards for asthetics....
My compensator (and i was told it had to be advertised as a compensator, not a slash hider/noise suppressor) was pinned and welded from the factory, no additional charge for mine on that, as it was a 14.5" so it needed it to avoid running foul of other laws... but i do think the threaded barrel is a no-no, or at least it could get you in trouble with certain things attached.
Of course, you can get in troube in NY for taking a cardboard tube from a TP roll, and adding concentric cardboard rings, and placing it over the end of a rifle... as that could be considered a home made silencer... if your not quick enough to jam it down your pants when to fuzz shops up. :)