I think a good regulation would be the good old times when they were using different type of tires,I think most of us here who are old F1 fans remember the days of the fight between Michelline and Bridgestone,where in cold weather Michelline behaved better and come earlier to temperature while in hot weather was Bridgestone doing so,the rule back then was that the teams should choose the tire at the beginning of the season and stick to it for the whole season no matter how bad this tire would impact the races of the team.
I think I have had enough of tire monopoly from Pirelli or any other brand,they should let the teams choose from 2-3 providers and let the competition rise,it looks like FIA does not give a damn about competition anymore.
I think they have already said in the past that there will never be a duopoly for the tires again as the competition too pushed for the tires is a safety problem.
It has already happened once in the past in the United States Grand Prix in Indianapolis that we had only 6 cars at the start because the remaining 14-16 were not safe for risk breakdowns.