Personally I would really like them to use values from RL type cars. The cars should handle like a similar could would, in stock form if you could buy it. The "stock" set should be unchangeable and there should be a serverside option to force stock setups for the cars, so one could create a stock vehicle league or what have you. Marshmellow suspension, understeer city, open diffs on most of the cars etc.
Personally, I think this should be the only set that comes with LFS and you have to modify the stock vehicle to make setups (or downloaded them or whatever).