I don’t think I understood everything: we have to enter production cars only? or we can make racecars or modified cars?
If we makes only production car, I think we shouldn’t go over sports tires for a car who is under class A.
And what is the metric ton thing?
Yes that’s the idea, i think it would be unrealistic to have a car on more than sports 0 tyres up to class A. Class S I think can use semi slick 0, and class unlimited can use anything.
I was also hoping that cars up to class S should be road legal for their time and all that but I’ll largely leave this to people’s idea of realism. This is more a hotlap league than a Gran Turismo lineup.
Also 1 metric ton is 1000 kilos just specified for those who insist on using Freedom units 
So any car in every category should weighs more than 1 ton?
I ask this because we can’t do a light sportscar of an average 130-150hp and less than 1 ton, like the swift sport or an 90s sportscar in class D :c .
No no nothing like that, just the power to weight ratio. So if you had a 500kg car if it has less than 100hp it’s class D.
Edit: if there is sufficient demand for stock K cars and superminis and the like which typically run less than 100hp:ton then maybe we can have a class E for those.
Oooh ok, it’s 200hp per metric ton! it’s all clear now thanks 
PS: the E class could be for old underpowered cars c:
Update: with the help of some others who are better at Google Sheets than I am, I’m getting a sheet set up so the information can be reliably sorted. That’ll probably take me a couple of days but then hopefully by the end of this week we can start proper.
p.s. in the meantime do check Boost’s challenge out, it’s similar but also very different and more competitive.