Yeah, I'm all for limiting the setup options on cars like the RAC, MRT, FB1, FBM.... those are real cars, after all!
Also, since we have limited the "steering lock" because "no real car has that much" we should also have some of the things be limited more.
however, for the street cars, I will sugest this mid list:
Aftermarket wheels/tires (hence size(unsprung mass) and width be modifiable to a certain extent, and have like, Auto-x slick coices, Advan Ao48 equivalent choices, down to high-preformane all season tyre choices that should "techically" last 40,000 miles.
Maybe the brake bias and force should be set to best possible and locked? dunno, so many things you could do with this stuff, yes it MAY sound unrealistic, but then, you can mod a production car to have this range of tunability.