Problem with doing that for SS and production would be location of safe areas. The mag gauge, grab a mag slide it in and your good to go. With production/ss and weighing and the box, you going to go to a safe area to do it. If you want a good random gauge of the mags, pick the 22/23 round stage out for the mag checks. If someone is going to be using a mag that really really pushes the envelope that is the stage its gonna happen at.
Checking at chrono would be possible and not take too much time you you basically had 2 "stations". While the shooter is on deck for the chrono, the mags could be gauged.