The suggestions previously were much more complicated. Also, it isn't about dividing weight classes. It is about making sure each person on each team is similar in weight. If there is a team with 4 150 lb people and a team with 4 200 lb people, the 150 lb people are nearly guaranteed to win. As you said, being light is an unfair advantage.
We're on the same page about advantages and such. I realize it is about the improvement. That is why I mentioned it. To be honest, I just can't see a seasoned veteran making equal gains in weight over me in just about any lift. I've only been lifting about a year or so, and have tons of easy gains still to make. Most people here my weight are even weaker, which means they have even more potential..