I see the appeal of the idea. You want to see which cars to loot without getting close to each one. Two hurdles I see are:
  • The cars would probably have to be remodeled with the doors as separate pieces. The devs save polygons and ultimately give you a better frame rate by modeling a car as one continuous blob, with no articulation or interior.
  • The cars are already some of the largest multiblock objects in the game. They’d be even larger with the doors open, which may cause issues with zombie pathing, as well as the doors sticking through nearby blocks in cases where cars were placed into tight fits.