1) Engines. [..] Keep the current V6 hybrid regulation in place, but take away the limits on fuel flow - just give them the amount of fuel to race with and let them decide exactly how they want to burn it. Keep reducing the fuel tank size every couple of years to encourage development.
2) Aero. Ground effect.
3) Chassis. Shorten the maximum permissible wheelbase, but keep the crash structure regulations at the front as they are. This will mean teams have to make their bodywork wider in order to get all the components in, increasing drag and therefore increasing the effect of slipstreaming.
4) Suspension. Allow active ride. Widen the track of the cars back to the 2m it was before the '98 season.
5) Wheels and tyres. Wider rear wheels than now, keep fronts at current width. Open up the competition to other tyre manufacturers. Get rid of the 'must use both compounds' rule.