Issue with the track designs, especially with the narrow tracks later on, is that the inside of corners is a sharp corner which is very unforgiving (and not realistic).
possibility: to prevent the 1 step forward and two steps back, one of the new bikes should have zero changes to maintain the progress.
Also, the scores should be split across the retirement phases and log a 'Last' score as well as a best. Maybe have splits, so 'best lap' as well as best full time.
I like this idea, maybe will do something like that