Yeah I think the biggest issue there is that its unclear to everybody because of the current ATF back and forth on the issue. People have been printing brace designs for years without issue so the only worry I would ever have is the position on braced firearms in general, not specifically 3d printed ones.
The newer versions of cura allow you to generate a random jiggle in your outer wall gcode to create that texture. Its pretty good and you can set the parameters on it for more or less intense grippy surfaces.
I totally agree with you on the nozzles though, I intend to grab a .6 and a .8 for this printer. Do you usually print in .6?
Yes, I'm almost always printing in 0.6mm with 0.3mm or 0.35mm layer height.