As title, perhaps a built in benchmark could be implemented? Obviously gives people the benefit of seeing the results and showing off the potential beauty of the game (Setup/settings dependant). But additionally, built in benchmarks can often be used in large media outlets, youtube channels (Think Gamers Nexus) etc, and this is a good form of advertisement/discussion promotion.
To work as a real benchmark, it would have to have the player car using player car physics with the others using the simplified physics as when playing the game. Otherwise it would be just a graphics benchmark. I don't know how much difference there would be to just a replay, but would like to see it.