The one thing I will add is that parity is possible in this situation IF there is something that is a true performance limiter for the class. That what small tire/radial classes were supposed to do, but then specialty track prep pretty much eliminated that as a factor. No prep does the trick, but no thanks.
But in classes like pro mod, factory stock, etc., there will always be one combo that has an innate advantage under the current rules package, and once people figure out which one and refine it, everyone will flock to it because no one wants to be at a competitive disadvantage just to be different. That, or deal with the headache of constant parity adjustments.