Looks like 4 classes should be run from what I've observed.
1) Stock to slightly modified HT motors. No expansion chambers, stock CDI with plug wire improvements(stock plug wire is garbage right from the start) no SBP shifter, single speed from motor to wheel or tire. An honor system is needed to prevent internal port mods and other such shenanigans. Too many mods move the bike to;
2) Modified Class HT motors. Open for hybrid top ends based on a HT base. Run what ya brung. Single speed, also
3) Exotic Motors. Morini's, Puch, Motobecane, you know what I mean. These motors are in a class by themselves. The over 9 HP motors make the HT Chinese motors a joke. It's like trying to run a Formula Ford in Formula One.
4) Electric bikes. With the ability to simply plug-in more power when needed and the possibility of modular battery and motor mounts to make change-out of components fast these bikes will rule races unless it's an endurance race.
Basically you can run them all together, it comes down to scoring then and if every entrant had to have a scorer then that would simplify things, no scorer, no race. The scorers would count randomly drawn numbers to count laps for, even if that mean's your worst enemy's team has to score you
The Proto-type cars run with Modified cars at the long endurance races like Daytona 24 hrs and LeMans so we can do it, too