Michel
My suggestion is to set a restriction on replacing the engine. This would contribute to the competition and makes is it more fun from a strategic point of view. If you can only replace the engine every 4/5 races cooling becomes instantly more important in maintaining performance. Furthermore it gives newer/weaker/less whealty teams an opportunity to be competitive more often.
That would be very interesting, but like all suggestions, it should be optional in the league settings.
In addition to an option to turn off this engine change limitation, an engine change window option must also be placed, varying between 2 and 5 runs.
As for the reduction of IGP billing, it is enough to increase the recharging time of the engines by suppliers:
change every
2 races - 30 races
3 races - 35 races
4 races - 40 races
5 races - 45 races
It's even a way to increase earnings and set a use for spare tokens!