Scott, I think you are worrying unnecessarily here. The object of the exercise is to slow down the new drivers so they have fun, but don't wreck their cars. Whether you do that but turning their throttles down, or enforcing a lower gearing, it doesn't really matter.
I doubt we will junk the ProductionCup. If no one uses it now, that doesn't mean it won't be used ever. Most people buy a GT12 and a diff anyway, so then it is just a case of what motor they run.
Have you thought of doing a rental deal for the new drivers? You can get some pretty cheap 17.5 motors now, so if the Club invested in them and then rented them out to drivers for a couple of quid a night, that would soon pay for them.
That way it is even better for new drivers - they don't get to shell out for a motor at all, and once they do they can decide which one it is. With the long life of BL motors these days, and the lack of maintenance needs, I wonder if you and considered a double helping of cost saving for your new drivers this way - no motor to buy and a slower car reducing damage to tyres and bodies? (I also think if you decided to do this and approached a friendly shop or distributor, you could get some discount for a bulk buy.)
Lastly, fixed gear ratios - not viable with foam tyres. To get a fixed ratio needs a fixed tyre diameter. Those able to afford to buy a new set of tyres for each meeting will have the tallest gear ratio and the fastest car. Fixed ratios work if the tyre has a fixed diameter, like rubber tyres in TC and karts! HTH
