Suggested

Driver injuries

Your driver could get injured occasionally. They could be given a random injury and they would have to take a few races off to heal. This would make reserve drivers useful and also add another strategy call for your team. 

It could also lead to differnt cars having good races and bad races. 

Would create some bugs because of some teams having no replacement driver, I think it should just make the driver's talent be half of what it usually is.

Or just force a team without spare drivers to drive with a car less for some races while the driver heals.
Maybe even both drivers can get injured at the same time. Like swollen eyes from looking at eachother funny.
In which case both drivers cant see but still have to drive the race. Which could lead to some crashes with yellow flags.
Maybe a fire in the engine could set back your acceleration -10.
And if u crash there should be extra costs for the crane and security personel to clean your mess.
Or maybe a broken wing could alter the car-aerodynamica in such a way where it is actually faster than a 'perfect' car.
Oil spilling from a crash could also be fun, as the oil can make a lot more cars spin out control and crash, injuring more drivers.
Or what about two drivers that were in a crash having a massive fight over whos mistake it was.
And then ud have to put out a press release apologising for the behaviour.

Ye, great ideas
But if u ask me, none of that please.

No words, brilliant one mate