While the ATF may allow mere removal of the brace or addition of a longer barrel to equal compliance now,...there is no reason to trust it won't alter things once again. At some future point, ATF may decide that possessing both an unmounted brace and pistol to be "constructive possession" of an SBR, just as they do with components of machineguns and suppressors. It fact, is it out of their nature to not do so.
I am NOT advocating compliance. But never forget their evil nature. Never expect reasonable.