Firstly, I thought that this is another thread related to cruise servers and blah blah blah but fortunately I kept reading and in fact, I like the general idea with the credits thing. Well, it could get some polish, but the overall concept is quite celver, to be honest. If you race, you don't crash that often, so you have credits to get repaired if you accidently crash (or get crashed).
This way, racers will be racing and wreckers will self-eliminate. Quite a clever thingy this is
Maybe the only thing that I would change is the "credits", because, as the original poster mentioned, it has a certain RPG feel into it. Maybe something more technical would be more appropriate. Or lets just be simple:
"You have 4 repairs left today"