Mark
My first objection to the motor proposal is that it is unnecessary. If it is an unnecessary rule, it is a complication. We do not have any motor problems now. If one develops, we can select a replacement.
As you state your proposal, the Piranha would be substitutable now for ANY slot.it Group C or various NSR motors. that is a complication for a stock class. Even if the Piranha is comparable to those motors, if there is a chance it might perform better, racers will want to check it out. Nine dollars for an unnecessary motor is nine dollars the racer does not have to spend. The spec you mentioned for the Pirahna is a 2,000 rpm range. That is a lot, and probably worth checking against the stock motor, or buying more motors to see if you can score a good one.
Our yearly series try to have a mix of spec-type box stock classes and open-type classes. The spec series are easier for new members to set up. If we start adding options to the spec classes, they become less spec.
Russell