Suggested

Race ban at 107%.

Some players sometimes don't race.  But their cars are still released on the track by default.
I suggest that you consider the possibility of making sure that cars that have not passed 107% in qualifying are not allowed to race.  Without setting up the car and strategy, inactive players will not reach 107%.
It will also help unload the server from the load to control the car without a player.  If the manager is playing offline, setting the settings and strategy will give the opportunity to enter 107% and his cars will participate in the offline race.

Just kick the inactive from the league, problem solved

But then your taking out promotion or making your league so low in numbers it cant grow anymore...

I am not disturbed by inactive players. The league will remove them itself. This is a proposal to give interest to the game.