I like the idea of running one class per vehicle type. Yes I am a nitro racer, and have only just joined the electric ranks with an RTR SC10.
If numbers per class can increase, based on running only one, then it can only improve the fun for all involved.
With the 1/8 brushless stuff coming out, there appears to be open slather on what guys are running with KV ratings and 4S/5S/6S lipo's. Why not consider a similar thing with 1/10, except place a motor limit on it as stated earlier.
2wd buggy, Truck and SC, all being 2wd, will probably be easier to drive (for less experienced drivers anyway) with a bit less power and 10.5 seems like a good compromise.
4wd, I guess being the flagship class perhaps can have no motor limit as it appears to be the elite, having said that, there have been instances more than once that I have seen and heard, of a 17.5 equiped "stock" 4wd buggy turning laps times that are competitive with the mod guys anyway.
At the end of the day, if the classes numbers can increase, then I'm all for it, as I'm an RC enthusiast, and enjoy all, and I mean all aspects of the hobby, and dont want to see anything detract from the hobby.
Cheers