Hi Des, I agree with you wholeheartedly. On reflection today, the 6.9 apart from its mechanical specifications, could never be considered a true 'flagship' of the 116 range. It just wasn't different enough to the other models in the line-up.
Forgetting the penalty of import duties that would have been levied on a car imported from Germany. pricewise the 6.9 and the Rolls Royce were about on a par. Given that the Roller had a somewhat nicer and probably more expensive interior, the extra money required for the 6.9 had to have its roots in the mechanical specifications and the degree of engineering that Mercedes Benz was always notable for.
One should also take into account that the late '60's and certainly the '70's were all about safety, safety and safety. Hence, the thickly padded doors, knee pads, horn boss and the absence of real wood, except for the slider switch panel which is indeed an absolute work of art, and real wood.
Cast your mind back to the fities and sixties - 300SE Coupe, all leather and again real wood. Then, the 300 Adenauer in all versions, i.e. Saloon, Fixed and Dropheads, the 220 Cabriolet of the Ponton variety - all real items of intricate interior beauty. But certainly not safe from a collision point of view.
Within the next few days, I am hoping to add more to this post on a more thorough scale. Regards Styria