I think it would take 1 minute to have each wrestler step on a scale prior to their 1st match.
It wouldn't be the actual weighing that was the problem. It would be the failure to make weight. This would screw up the brackets etc. etc. Can you imagine the whining that would take place on here if someone drove 100 miles for a tournament and then everyone in their bracket ended up scratching? The problems it would create would be endless.