Resetting the career / new save

I would like a feature to reset campaign progress in single player. Now that I have beaten the game and got several cars to 399, I'd like to be able to go back through the game (just like I did originally, not by figuring out and selecting which missions I think went in what order) and replay the game with my new cars. This would add a ton of replayability for me personally since, I could pick cars I like for each class and run a new game with each of them. 

I know there is an option to delete something in your save data, but I don't like that option since I would be starting over completely and lose the weekly cars I've unlocked, the ability to earn shipments, and all the cars I've already unlocked and built.