Everyone keeps saying that the majority of riders are in the amateur ranks and can already un CC for CC, but they are missing the point. Only the wealthy or sponsored/supported by someone else can afford to race in the 450 class and why would anyone in the amateur level that aspire to go pro even consider riding a two stroke if they are paying for everything themselves? As soon as they get a shot to go pro, they would immediately have to go out and get a 250f, and spend thousands getting it up to competition worthiness. It just isn't fair to have to transition from one bike to the next just to move on to the next level.
I would be perfectly happy just to allow CCforCC in the 250 class alone, because then the end result would determine if the 450 class should just be an open class. If 4 strokes start getting beat by 2 strokes, then the 2 stroke development cycle would open back up to more modern bikes by the others (maybe not honda).