That "all cars in class get same performance" in undoable. Not even F1 games can get it right.
Most you can do is give them same power and overall grip, but things like different wheelbase will still make every car handle differently. Anyway "same power" would be nice AS AN OPTION in race lobbies.
Maybe very slight differences. To make the cars competitive in their class. I'm glad that the new cars we got are good for racing and not too good or too bad. Just right. They should have done the same with the Roosevelt.
It wouldn't go as an option in races, just an overall tweak.
I wouldn´t really want all cars in a class to perform the same in free roam or in all races. You lose cool chances for handicap races and in the end crew organized uni-car races would all feel the same. I like every car being different.
Being able to equalize them with a toggle when you wanted could be nice sometimes, it´s a cool idea... but I wouldn´t want it as a permanent change.
Congrats on the OP even if I don´t agree with everything, lots of work and some nice ideas there!