[MetroMPG]

It's not a bad idea.

Couple of issues: Don't forget the cutout has to accomodate the movement of the wheel with suspension travel too. So it can't just be a simple circle.

Also, the wheel cover/tire on my car isn't flush with the surrounding bodywork. It's recessed at the top & sticks out relative to the bodywork below the center of the wheel. Makes it more complicated to design a gap filler with smooth lines.

Ever see the "bristles" on transport trucks above the trailer wheels to keep spray down? Maybe that could work as the "gasket" bit that has to permit the tire to pass through when turning.