The way as you bring it is not much fun I think, because of people leaving and joining all the time.
However, if we can make this as a mode.. then people can join and you will be more sure they will stay all 10 races. So you will race with a group of friends for 10 races, just 10 random races of our server, and the best wins after 10 races. Maybe you could select a car for all 10 races.. of several cars. Or race lenght.