If you can get a signoff easily, I'd go for it. For just a SBR, I don't know if incorporation makes sense though. Once registered, you can use any length on it you'd like and in any caliber. Thus if you originally have a 14.5" M4 upper on it, you can later put a 11.5" upper on it, or maybe a 7.5" 9mm DOE upper if you'd like. For something in the 11.5" range, I'd use a 9mm upper rather than a 5.56 as it doesn't need the velocity. Bt thats part of the beauty of the SBR - once its registered you can change upper configurations, lengths, and calibers as you wish. Try one config and if you don't like it, just get another uper and try someting different.
As to moving NFA weapons; as long as its in your home state and there are no local laws or ordinances regarding gun transport or possession outside of your home/property, its just like moving around with any other rifle. If you're going to cross state lines, however, you need to first get approval from BATF to move it interstate by filing a form 5320.20. Unless you intend to go to a state where possession of the SBR would be illegal, BATF will approve the application. It usually takes about a month for processing, but you can get approval to move the weapon interstate for significant periods of time (I think 6 months is the max).