Any muzzle device used to extend a barrel to 16" overall in order to be legal must be permanently attached, ie. pinned and silver soldered or welded. You can't just screw on a suppressor to make it legally a rifle. If you're talking about the Baja 5.56, it looks like it is designed with this in mind. With just a quick search, I wasn't able to determine if the Baja can be disassembled for cleaning from the front cap. That's a feature I would consider desirable for a permanently mounted application, otherwise cleaning the gun could be an issue... you wouldn't want to get a patch stuck in the baffles...
Something else to consider... a short barreled 5.56 suppressed is NOT hearing 'safe'. A suppressor will reduce the muzzle blast to the point where you won't do permanent hearing damage with 1-2 shots, which is absolutely possible with a short 5.56 indoors. You may also have issues with the gun being over gassed with the standard gas system. An adjustable gas block will likely be required to tune the gun to run properly with the suppressor mounted.
