i think you miss the point, i know what you are saying, but these cars (most of them) actually are opel, they literally deliver them as opel/vauxhal spec and holden sticks their badges on instead, thus how you can order the car without the badges installed ( i inquired with holden :)).
the nissan pulsar-holden astra
mazda 323-ford laser, are not identicle cars.
different tail lights, headlights, grills, interiors ect.....