Well, on the topic of combining classes, let me say this. Take a look at the American LeMans Series. They run four different classes on track at once, and the speed difference from LMP1 (fastest) to GT2 (slowest) is pretty significant. This obviously means a ton of cars on track at once, but it also means some pretty exciting racing happens, IMO. 8) It can comepletely change any given situation/strategy sometimes, and there’s plenty of overtaking action.
Granted, Karts are a completely different story…there’s not nearly the room on a kart track as on a big track like Road America or Sarthe. Just some food for thought, though. 🙂