Reminds me something I did in one of Saints Row games :)
Music and sounds definitely improved the experience. Maybe some voice lines could make it even better but might be risky if they are not just right.
If anything could be added I'd say more "silly" or recognizible cars like Ice cream truck, Firetruck, police, F1 or even Batmobile :)
Would also be cool if after getting hit I could slow down time for 1 or 2 seconds to plan my next move.