Tires. Tires are how you do it. Spec tires.
Some good things that would come with spec low traction , racing. First, longer tire life, reducing running costs. Second, an emphasis on driving skill, with less traction you need to be more careful on the throttle, and braking. Third, a reduction on the "motor of the week", if you're limiting your car based on traction, the motor matters much less. Fourth, an empasis on chassis setup. Instead of seeking the most stable, and most consistant setup that won't flip, you'll be seeking the highest traction setup, even at the cost of some stabilty. "Fourth" would also lead to more interesting racing.