Some of my thoughts:
I disagree with the drag reduction, if anything I believe an increase in overall car drag is necessary. However, care must be taken to ensure the regions of turbulent airflow - and generators of the turbulence are carefully situated to avoid detrimentally impacting the following car's front wing.
I would widen the car's track again, and make the rear tyres have twice the frontal area they do now (i.e. wider and taller). The front tyre size would remain fixed or get smaller.
In my opinion a major problem with modern F1 is that viewers cannot see how quick and good the drivers are. Hence my rule changes are aimed at bringing ye olde powerslide back into vogue.
If the public see the spectacle of the finest drivers in the world having to drift their way through corners (as its the fastest way), then overtaking is not as
important, but it should be made easier anyway.
In order to make this (powersliding) possible, an aerodynamic configuration that works well in yaw is necessary. Thus, the rear wing endplate sizes would be cut drastically (this also increases downforce at a level high above the ground plane - a good thing).
The diffuser would be banned... totally. A maximum gearbox and sidepod frontal area through several sections would also be specified to ensure a good flow-rate of air through the suspension and toward the following car.
The aforementioned tyre size changes are there so even when sliding the car around, wear rates should be under control (these tyre sizes [slicks obviously!] can be fine tuned as necessary).
The front wing would be moved back toward the ground plane pre-2001. With the tyre changes and the diffuser ban, it may not be necessary to make it moveable... but that is open to change.
The various winglets around the car would be banned through extension of the closed section ruling currently used for the rear wings.