Went to Las Vegas this year, and it was boring. They all drive the same car, just different stickers and such. Get rid of these spec cars! Make them drive a body shape available to the public.
No splitter, no spoiler, no tacked on aero aides. Make them slow down and accelerate out of corners rather than just follow each other single file hoping someone will screw up. You will not need stage racing if you do this.