Adding in engine capacity division between classes is too hard to regulate, too easy to cheat. As for putting a car into race class for having a wing, that's a bit crazy - what about other aero such as undertrays and front splitters? Do you count them as well? So take a stock 4WD car (i.e. Evo, GTR) with aftermarket wing, under those rules it would be in race class. Not exactly fair.
Keep it simple, make it fun. I'm sure Russ will come up with a good formula to run the proposed event.
Although I do agree that whatever the rules, if people want to win they'll pump alot of $$$$ into a car and put a decent driver behind the wheel