For example, my car towards the end of the season is 100% developed.
If, at the end of a race, my car's condition degraded from 100% to 87% and engine was 93%, I could see on the Repair page how my car was currently performing in each design attribute due to the wear and tear present on the car.
This might mean my car's current condition represented under each design attribute might look like this:
Technical Director "Our car will perform near perfect with the present wear on it."
[91] Acceleration | | | | | | [98] Fuel Economy
[93] Braking | | | | | | | | | | [92] Handling
[82] Cooling | | | | | | | | | | [91] Reliability
[85] Downforce | | | | | | | [90] Tyre Economy
Once fresh parts and/or engines are applied to a team's cars these values would increase to the original performance. (In this case, all 100 since the car is fully developed)
Cons to this idea are it's kind of complicated for players to interpret it.
Wildly conceptual idea. I'm crazy.
