There is a fine line between the realism and the effectiveness of certain features in a game, sometimes the developers just have to make a compromise.
Things that definately need to be in for the 5 year plan of the Grand Prix series (that to my knowledge arent in GP4) are:
Safety Car - When it comes out you should have to actually control your vehicle behind the SC, games that make you go into auto-drive are really poor, it would be cool if you were leading and the safety car pulls in and lets you set the pace over the line.
Restarts - After a large crash within the first lap, the race should be re-run, with those competitors either returning in a backup car, or out for good.
Stop-Go Penaltys - Including crossing the pit lane exit line, speeding in pit lane, dangerous driving, passing under caution, and jump starts.
Track Details - Full catchment fences, deformed gravel traps after a vehicle has gone through them, tyre walls that engulf the car instead of bouncing it away,
Crash Physics -
1.) Tail/nose whips when a car hits the fence (think of Australia 2001 where the marshal was killed in the accident with Villeneuve and Ralf), its the one thing that annoys me in GP3 when there is a realistic crash, is when they make contact with the wall, there is no inertia or calculations done, the game simply rebounds the vehicle away on the angle it hit on, and in one word it simply looks 'gay'.
2.) Vehicles launched into the air after decent contact with the rear of another vehicle, this is not generally caused by the contact, but by the air expelled from the car infront suddenly hitting under the following vehicle which just lost its front wing therefore its front downforce and resulting in that car lifting off the ground.
3.) Scratches and tyre marks after contact with other vehicles or scenery.
4.) Broken wings are blown around by cars driving past.