I'm using PC for managing races and lately I have thought that it would be easier to manage my cars if there are keys for changing push levels - like there is keys for using KERS (S + K). As many already might know you can improve lap times a bit when push level on corners is high and push level on straights is low. So with my suggestion you can more easily manage two cars at same time with keyboard.
My suggestion for there is something like keys 1-5 for driver 1 push levels and keys 6-0 for driver 2 push levels.
In example;
Driver 1
1 = PL1 (push level 1, lowest one)
2 = PL2
3 = PL3
4 = PL4
5 = PL5 (push level 5, highest one)
Driver 2
6 = PL1
7 = PL2
8 = PL3
9 = PL4
0 = PL5
Keys of course can be differents, i.e. like Q,W,E,R,T for driver 1 and Y,U,I,O,P for driver 2.