I think F1 should be open to both 2 car and single car entrants. Single car if you don't have the finances but you can still make it if you have a good design team. Also it should be open to as many teams that can put a car on the grid and qualifying becomes just that, the top 20 or so cars get to start the race. If a top team has car troubles they may miss out on the race.
The other thing I would like to see are some of the restrictions removed to allow innovation, this used to be used by car companies as an advantage in their manufacturing and sales. One I would like to see is engine size and configuration, instead of specifying the engine and recovery system it would be better to specify the amount of fuel you can use for the race and qualifying and allow the engineers to come up with the best and most economical power unit. This type of technology can then be feed back to the car companies, in turn they can become more involved again.