I've had some ideas on sport mode, some of these will be controversial others won't be well thought out (I typed this half asleep on a hot bus):
Get rid of SR related resets: Driver rating should not be connected to safety rating, PD don't see that a reset is actually a reward for those who want easy wins. Taking that system out will clean up some of the deliberate dirty driving. If somebody wants to be A+/D then good for them.
Automatic time penalty for crossing the pit exit line: Honestly this doesn't cause too many incidents but it's a lack of respect to anybody else on the track.
Continue to match based on SR but set limits: At the moment the game will fill the top lobbies with SR99, sometimes that means an A+ grid will be filled by a few D's at the back. If the game can't find enough players within 2 DR levels of the lobbies top use lower SR to fill the grid (A and the lower S numbers). That would give the lower ranked players a chance to race for good results.
Stop people from deliberately starting at the back: This is more of an American problem than European because the driver skill is a lot more spread but it causes a lot of crashes, they're usually the lower rated players fault because their driving is less predictable but that's why they're a low DR, they're not supposed to be good drivers. If people don't have a qualifying time the game can use their FL from the previous race.
Collision Penalties: Make these a lot like the track limits penalties but in reverse, if there is contact but neither driver has lost time to the cars around don't penalise them (this will help bump drafting too).
Add pitstops: There is no sense in having strategy races when some circuits allow you to make a tyre stop and only lose 3s to the cars on track (Bathurst I'm looking at you). Realistic pit lane times would mix up strategies in the longer races.
Mix up the races: We never see anything quicker than Gr.3 in race B, let's try the occasional Gr1/2/SF sprint race, it might be fun.
Make provided cars an option not compulsory: A simple one for race A, if you don't own the car you can still borrow it from the game otherwise you can race your own with your own paint scheme.
Penalise driving, not DR: There is no need to have players DR factored into the penalty algorithm, take it out.