Maybe an easier one would be mandating that cars should not be allowed to have open-air transport areas, for safety reasons such as transport not sticking out, pedestrian safety, and so on. Since it's possible to stick out with those pickups, that automatically prohibits cars
What also can be added, is abolishing the lease for SUVs altogether, and prohibiting the import and building of those that are taller, longer, wider, and heavier than certain dimensions (say 4 by 1.8 by 1.5 m), even for work.
Mandate that people sell them. Those who bought the SUVs before 1 January 2025, then can get a subsidy of 25% off for the new car, if it's more energy efficient, smaller and lighter, and doesn't have an open rear. Or, they can get 50% off for a bike (electric, transport, or whatever, but no fatbike).