If uncomfortable with the bullet button, then pull it. You are going to have to anyways. Note that you could buy a complete lower assembly today (and get it later) with both a standard release and adjustable stock. Again, something has got to change before assembly. But the lower assembly is not restricted nor would an upper. In the good old days, you could swap uppers and lowers all day and it didn't really matter (assuming you didn't mix rifle and pistol parts, etc.). Not that it couldn't happen but I've never run across any hall monitors pointing out that, "Hey, you can't put that upper on that lower." Although I suppose a gun store might mention it if you bought the two at the same time. And they might not want you to fit them together to see if they fit a particular case or something. IIRC, my last purchase was papered over with some notices on the receipts, etc., that they weren't responsible for any changes made by a customer, etc.