As far as the calender goes, I don't think Formula One needs another race in Sand Land, and as far as I'm concerned, Bahrain should be dropped. I don't actually mind Abu Dhabi, but not as the last race of the year. I don't think Russia will last long; Putin may pay and pay, but even the organizers (Bernie) have people in the West to answer to. That's two down, let's see what else can go. Malaysia's Sepang Circuit is actually a pretty good track, but Singapore's street race just looks like right angle turns through a concrete wasteland. It either needs some major improvement or it needs to go (my preference). Germany MUST be brought back to the schedule, and quickly. I've never liked the new Nurburgring track and now I dislike Hockenheim since they demolished the long runs into the forest, but until either a new track can be built (that isn't all hairpins and right angles) or the existing ones are made better, run it at Hockenheim. And make either Brazil or Monza host the final race.
My big changes would be made to the cars. I'm sick of these high downforce winged cars where aerodynamics are so important. These cars can corner at astonishing speeds, but they can't run closely to each other without losing grip and can't pass without resorting to stupid gimmicks like opening flaps and battery boosts. Their hybrid powertrains are heavy and expensive, yet they don't work as well as the one in a Prius. If it were me, I would ban all of the wings, diffusers, and other aero aids such as movable bodywork. I would force the teams to place the radiators in the front and enforce a minimum ride height at rest. The cars could not produce more than 200 or so pounds of downforce at speed (enforceable via a portable wind tunnel and a scale at each race). They would have a requirement of three liters and no turbochargers or superchargers, but they could configure their engines however they like, with number of cylinders, weight, cylinder configuration, and such up to them. They wouldn't corner as fast (which would make the new tracks with their tight turns in need of some changes), but their straight-line speed would be higher and they could actually get near to one another without worry of loss of grip. I think we would get some real racing back.
My Own Bad Self.