Your post made me think. It would be cool for a tourney to have a scramble on another mat with the kids that were bounced. An organized scramble with a ref or maybe one of the coaches to score. Nothing official, just to get kids a fresh opponent.

Having a scale at each mat before each match would cost chaos. Just teach your kids to have that goal weight. One of the great things about a morning weigh in is the celebrated breakfast or snack.