This is my suggestion for BITD classes
1) Pro Production N/A- Rules remain basically as they are right now, (Note: All involved Oem's still offer a high performance N/A model and the majority of the existing class racers are currently racing these models.)
2) Open Production Pro- this would replace the "unlimited Class" However make changes to bring this class back to a more production oriented class. Factory and aftermarket turbos allowed but no motorcycle/snowmobile engine swaps or complete chassis. Make all other rules basically the same as pro production. Existing "unlimited" cars who have raced in 2015 could be grandfathered for one or two years. (there are really only four or five of these cars and they have not proven to be competitive)
3) Sportsman- "Run what ya brung" Under 1000cc and utv body, must pass safety tech. If you want to creat some crazy buggy with a UTV body, or you just want to come out and see what it's all about in your near stock UTV this is your class.
with this plan the entire pro class is "production" based and you have not slapped the existing N/A racers in the face. The OEM's can enjoy seeing both of their Performance models (turbo and non turbo) competing on a level playing field. Sure there are going to be new models from other OEM's coming in the future (or now for that matter) At this point I think you put them into one of these classes. Turbos in open class and N/A in Pro N/A. The current rules do not exclude any type of transmission. it just states that you have to use the stock transmission so right now the new Yamaha is legal in the Pro class by all rule definitions.
I think this would be a better plan than what is being proposed right now which is basically telling N/A racers that if you don't want to race against cars with 40% more horsepower then you can go race in "unlimited" . Seems kinda dumb.