I would start with a powerplant, and my personal preference would be a gas turbine generating somewhere around three thousand HP. Since gas turbines take time to spool up and down, a complex CVT transmission and KERS system would have to be developed to deliver optimum four wheel drive. Or maybe eight wheel drive, don't let existing rules limit our imaginations.
The body would be fully enclosed, with maximum ground effects. Additionally, large variable pitch wings would be mounted front and rear, to add extra downforce, or set at zero incidence to allow maximum velocity. I was also thinking of clamshell doors on the engine exhaust to direct forward, rearward, or sideways.
Imagine accelerating, jet exhaust pointed straight back, maybe some afterburner thrown in for extra, wings set neutral, and all four wheels digging hard. On braking, wings set at maximum angle for downforce and drag, jet exhaust pointed forward, and brakes glowing.
Hey, if it works on the Eurofighter, why not a car?
Racing should be decided on the track, not the court room.