“If this flies they could probably do it with any other feature... like pistol grips or bayonet lugs.”
I don’t think so. Short barreled rifles were banned by congress in the NFA. That’s the core of the problem. Determining whether a brace is really a stock is relevant to the (bad) NFA law. There is nothing in the NFA about grips, flash suppressors, or bayonet lugs so it would be an an insane reach, even for the ATF to try to regulate them.
Repeal the NFA, disband the ATF, and then we won’t have these problems.
Yes, good point.