I have been in the hobby for some 30 years off and on. I have been more in 1:8th Nitro than electric and of course 1:8th is an open class. Run what u brung!
In my lifetime I raced full size cars which included Formula Mazda, then to oval dirt with midgets and full size sprint cars in the 360 and 410 classes. In all of these classes we had different manufacturing producing tires and they were available for the racer to choose manufacturer. Having the different manufacturers advanced the quality of the tires and kept prices competitive.
I believe spec tires opens a can of worms. The spec tire company is chosen by the money being they paid to an organization or by special sponsorship given to someone who makes the rules. However the worst part is the racer will be presented with over priced tires that don't perform as well as other tires in the market. If the same tire is consistently used the quality of the tire will not grow as other brands. (I am referring to RC Market and not full size race cars since we all know the quality of the tire for RC will not place a life in danger!)
To me you should just have two classes. One for the rubber tire and the other for foam tire. As an example, if the class is stock then the racer can choose any rubber tire that falls in the rules regarding size (etc) as we have now. If the class is open then any foam tire can be used. But the spec tire has to be forgotten. There are many manufacturers trying to make a living and offer racers good products today and better products tomorrow. Any rule making that stymies growth in quality is not good for any market.
I am in the tire market for the RC Hobby. However my tires are not any good without a car, motor, battery, radio and etc. 2.4 in radios, brushless in motors, lipos in batteries, would not have been developed and grown in quality if we just choose one company made it spec. Or choose any motor manufacturer as long as it wasn't brushless. We would have stymied growth in the rc market.
I think having cars built for new battery size is okay as long as the other rules are kept such as wheel base and width and weight are maintain for each class. But don't stop the creativity of the manufacturer and any other products. The F1 cars (Full size) don't look the cars of the 60's and 70's. But I am an F1 fan that will be in Austin watching racing next fall. Indy cars found out what spec does for their series and will see a great emergence in 2012 with more chassis manufacturers, motor manufacturers, and body manufacturers and lower pricing to teams! Allow creativity and choice is all I am saying.
Just my 2 cents.