There is really only 4 groups. The other 4 were created to allow a second entry at each event. Instead of racing once you got to race twice in 2 different classes. For example Superstock CR125 is the same Group as W/C superstock. It’s just there second entry.
Another example would be Yamaha Light and Yamaha heavy. Same guys race in both.
Could the 4 125 groups be whittled down some? I would think so but that would be up to the racers in those classes to figure out how without chasing people off. Aside from the fairing the biggest difference is the Formula classes allow ICC’s and modified 125’s while the CR125 classes are more “spec”