I'm going to go out on a limb here. I don't understand how pistol braces were ever legal in the first place, including as some sort of ADA device for disabled persons. (BTW, this thread is the first I've ever heard of that explanation.) A pistol brace is obviously intended to be used as a short shoulder stock. I don't think they should be banned because they can be used on an AR with a longer barrel (i.e. not an SBR) to decrease length of pull for small statured people, but beyond that, I can't see a legal path for them.
Someone mentioned braces and AR pistols as being on thin ice, and I agree. However, I'll add the Mossberg Shockwave to that list. I don't understand how that is not a SBS.
In fact, I'll go even further out on a limb and say the same thing about bump stocks. Those were an obvious attempt at obtaining full auto performance while narrowly remaining inside the line of a semi auto gun. No wonder the left wants to register everything.
Lastly, I'll leave some food for thought. Instead of spending time, money, and energy trying to circumvent well established laws, why not fight those laws in court? We finally have a sympathetic Supreme Court. Now is the time, and don't delay, to get these underlying laws overturned. Congress and the Executive branch have proven they have no intention of relieving us of these laws; the judicial branch is our last option.