How could F1 cars realistically be made any shorter?

I would love to see the cars shrink in size a lot more close to how they were in the 2000s. They looked and were more agile and the proportions just look right for racing car. In general, I don’t expect high-performance vehicles to be the same length as a full-size sedan. But with the safety standards of today and lack of refueling, what possible changes could be made to shrink the cars while not compromising the safety and shrinking the fuel tanks to the point where you have to refuel?