Buckeye, your thinking is very similar to mine. Measuring only pertinent arrows would be a huge help in cutting time. Because of the huge difference in distance attained by changing arrow weights We would have to assure somehow they were playing on a level playing field. One way to do this is as you suggested use a minimum arrow weight per weight class. This would leave the burden on the archer to make sure his bow came very close to the weight class he would like to enter. This is how we do it now. On the other hand if you wanted to encourage archers to bring thier favorite bows and not have to alter the weight we would be forced to use a grains per pound method.
The regular flight will be no problem, very few restrictions. Any of the trad bows could also shoot regular flight if they chose just as we presently do. We can use complicated methods for comming up with rules as long as they are simple by the time they reach the actual flight shoots.
Something I thought about for the trad flight is to eliminate weight classes alltogether. Only measure arrows that met a minimum distance goal and then after the fact weigh the arrow and the bow. If the arrow weight did not conform to the minimum required weight the shot would be disregarded. This would leave the burden on the archer to prepare for the flight shoot ahead of time matching his arrows to his bow. Not too much to ask.
Example might be that trad would be shot at 8 grains per pound, no arrows under 200 yards would be measured. After the arrows are picked up we verify that the arrow weight of his furthest did not go below 8 grains per pound and list his distance.