Sorry but I really think that's only possible for Online servers.
If even in Content Manager in offline quick races or weekends it is not possible.... it surely remained impossible with any other method.
The only possible method is use your own evaluation method to calculate how many laps can be done in a fixed amount of time..
Total time race in seconds .... divided with your ( or AI's ) laptime in seconds .... and you'll get the number of laps for this time.
Even not possible for your own pleasure to create such a private time-scaled server as you cannot add AI on servers.