A few things really, and i'll get right to the point.
In the garage, when you alter setups etc, how about an option for a corner/situation simulator? For example, you could choose to simulate a hard right turn, the car would then continuously drive a hard right turn untill you told it to stop, this could show you how your suspension/tyres would cope with certain conditions, the same could be done with bumps, for example 1cm high bumps every 1 foot, test your car on that to test your shocks/dampers. Also with braking distances, you could 'tell' the car to be driving at 140mph, and brake 100%, this could test your brake bias and strength to see if it will lock up, skid off etc. I don't know how hard this would be to impliment, but its an idea anyway.
A very simple one now, you know the race position box while you're racing? How about having the lap that a specific person is on next to their name, for example Banshee (1) etc, this would help alot as you could tell if the person infront is infact on the lap you are(so you could push more to overtake them) or wether he's the person in first:P(presuming you're not in second)
I had a few more suggestions, but I cannot think of them now, i'll add them later.