I'm more than willing to hear discussion on the subject, but it's my personal opinion that motorized recreationalists don't need to be divided to fight over already scarce opportunities. For instance, your thought is to separate side by sides from 4 wheel drives. This sounds fine until you consider a stock Suzuki Samurai, or flat fender Jeep, is not that much bigger than that side by side. If you want to REALLY split hairs you would have to make 3 or 4 classes just for 4 wheel drives.
I really believe strongly in multiple use of our public lands, and making another class of OHV's will just further divide users and limit our (4 wheelers) access.
Please remember this is just my opinion, and you know what they say about opinions don't you?