I got to number 13 in the world on one of the rivals challenges, can't remember which one now. And that was yesterday too, not like 20 mins after the console had been launched.
It was a fluke though
Hot lap table would be good, why not do it in something cheap like a 350Z and allow upgrades up to a maximum of C500? That way people can either go for power, or handling, or both, but it remains a sensible car that needs skill to get the most out of rather than just nailing the throttle? Good idea though!