Just a little thought, I think there can be some sort of a "slider" to adjust the importance and affection of different car stats to the league.
For example:
Accel, braking, downforce, handling: normal - x1, x<1 => less importance (this means the car performance doesn't different too much, like 10 DPs and only a very small difference), x>1 => more importance (this means maybe even a DP can make a huge difference to the car performance)
*note: this can only be doable if the devs can introduce a system that produce more variation in speed, as explained in the Dirty Air/Slipstream thread
Fuel, tyre: x>1 can make the tyre wear much higher (like a x2 and 4% tyre wear become 6%, I am not saying 8 because that would be too extreme). This can force players to invest more on tyre economy. Similarly, a 10 DPs difference in fuel can maybe make the car uses 0,1 litres more fuel every lap for example, which impacts the car's pace.
Cooling, reliability: increase them to maybe encourage players to invest more on their HQs
Of course, this system will be complex as it has to comprehend different league tiers, scale the difference correctly... But if a system like this can be introduced, that might become a huge feature for the game, as the league owners can do more "regulation changes" and creates new META, increasing the competitiveness and variation inside a league (instead of just waiting for the devs to change the dirty air or sth else, which might not suit some players). In a league with managers lvl 10 competing with lvl 20 for example, moving the slider down on certain car stats can bring the pecking order closer together, creating more entertainment for these low-level managers. In a league where players are mostly max-level with a max-upgraded HQ, moving the slider up may make them to play more strategically, focusing more on some areas that might be normally forgotten...
If this can be implemented, a whole new field of rules can be opened up later, like restricting the number of engines and parts (maybe 5 engines in a season or sth), flexible DP caps on certain car stats, etc
If there are any problems with my suggestion, feel free to comment and improve it. Don't criticise me harshly though :(