It doesnât take an auto historian to rationalize that Mercedes-Benz has not only created some of the greatest vehicles on the road, but also the specific categorical segments they fall under. Automotive Rhythms was on-hand when the Vision CLS concept debuted at the Frankfurt Auto Show in 2003. Ostensibly, it was to become the industryâs first four-door sports coupe. But a coupe has two doors. How would it succeed?