Part of the reason is, as you point out later in your post, that some points will always be in contention, not least due to the international nature of this forum and thus the need to compromise.
For example, in pretty much any place in Australia that has a petrol station, and this includes rural, inland, and remote areas, you will be relatively confident of finding 98RON. That being said, there are only a very small handful of cars that would ostensibly demand 98RON (e.g. perhaps the Impreza 22B, which is a rare model in itself). I imagine that the most rarefied of super and hypercars will also pretty much require 98RON too.
Furthermore, semi-slicks are also plenty road legal in Australia but don't expect insurers or cops to rule in your favour if you have a bingle with them on!
That being said, I guess we have to put a limit somewhere and most of Razyx's rules are already plenty acceptable for capturing the 'spirit' of what should be included. This will be the list I suggest:
- Fuel type 95RON max
- No semi-slicks
- No race intake
- No race exhaust
- At least one muffler of any kind
- No downforce undertray
- Minimum ride height 100mm
The 100mm comes from my local guidelines, feel free to come forward with your own values as this obviously may vary. I feel there should also be a minimum reliability figure as in the previous 'production' board, there were cars with 0.1 reliability, which clearly doesn't compute.
I've not included the limitations about the brake pads as they're already a regular (and optional) feature on sports cars, notably e.g. Porsche will offer them as an option across most of their range. I've also not included the limitation about carbon fiber chassis as a couple of production car companies make cars this way... but the relevance of that in the broader market and thus the appropriateness of this rule is debatable. I would still like to see some kind of class segregation system based on the components a car uses, or even their production costs.
In short, I'm still not sure.