In my opinion, the best way to make the aero work better in traffic, is to actually make it more powerful...
Think about it, that everytime the regulators try to restrict the aero stuff, they make the situation worse.
Restrictions result in the teams trying work the wings etc.much much harder to get grip, which make them extremely sensitive to disturbed air.
I believe more powerful diffusers are a key component, as they are much less sensitive than the front and rear wings. Of course we must not allow the cars to suddenly increase their cornering speeds, and that is the crux of the problem.....
The front wing has been correctly identified by others as the one we want help the most, yet the regulators have narrowed them, raised them, and issued a standard middle section. Sure the wings were widened 2 years ago, but the front wheel sitting behind it, just cripples it.
I believe the wings should be allowed to run as low as the reference plane, so they REALLY work in ground effect, making them still powerful, even when in the wake of a car in front. If they also allow a large area for the mainplane & flaps etc, ultimately, the cars will run with lower flap angles, in order to balance the cars balance. Lower flap angles work the air less aggressively, so are less bothered by turbulent air. Then, with these powerful wings, you can easily run a "traffic mode" flap setting, that will give a decent amount of extra front aero. Leave it up to the driver to decide where they want to deploy it, that way the passing zones aren't pre-determined as much as it is with the DRS zones.
Look back to when the late 80's and early 90's, when aero was REALLY understood, but the cars have quite a bit of aero freedom. There was consistently more close quarter racing, as the cars would still work to a degree in turbulent air......