As today we can simply buy engines every race Cooling is useless, why should I invest in it if I can simply start every race with a new engine?
How about we limit how many engines can be replaced during a season?
So here is my idea.
Adding a new option for the host to limit how many engines a manager can use during a season(only taking effect at the beggining of a new season).
Then a bunch of options starting from 5 (1 every 3 races in a 15 race league) to 11 (1 every 2 races in a 22 league) and adds an unlimited option (wich basically remains the same).
And to not let the managers be blind on it, add a label with "You can still use 4 more engines", both on repairs page and on the setup page.
I believe this way we can add new excitement, as managers will need to think when they should replace the engines, use it on the beggining of the season, trying to make the most points of it, or trying to make most of the replaces at the end of the season.