SCARY Cruise Control Issue!
2) A behind-rim mini-stalk (a la Toyota and many other Asian brands) must be located below the 9 and 3 o'clock positions so as not to interfere with steering rim access. This means having to move your head to look down, with repeated unnecessary distraction.
3) Due to the multiple functions of a single cruise control switch (more complex than the switches now on the wheel face spoke) the labels should be visible. A lower steering wheel location requires more of a change in focal length for the eye. The stalk position requires the lens of the eye to undergo less change for each refocusing. This also requires less time with eyes off the road and less head movement to look down toward the lap.
The OP informed us that his wife knew the location of the stalk, but somehow touched the wrong stalk and moved it, unlike the up and down of a turn signal, toward her. It is unlikely that, with even minimal attention, she will repeat her first time error.
True - this issue is now a focus, and will NOT happen again - BUT we were lucky that a serious accident did not occur the first time. If you are familiar with BMW (5-series), the cruise control stalk arrangement is similar in a rotary position (your crowded wheel face / driving distraction comments are well noted and agreed), but the axial position of the cruise control is farther away from the driver, greatly lessening the chance of grabbing the wrong one by mistake. Granted, there is no such thing as 100 percent, but a small change could make such a difference. We'll bring this up with the manufacturer - the point on this venue is to raise awareness and hopefully save another MB driver from repeating our experience! Happy Motoring!

Your point about increasing the axial separation would likely create the result you theorize. But, here is the opposite argument. Whether MB uses a 5th percentile female to 95th percentile male (or other range or midpoint) for hand size, it seems clear that the intent was to have both the speed control and turn signal stalks within finger range without removing the hand grasp of the wheel. I am a 95th percentile for male height, likely with similar hand/finger size, and if the speed control were moved forward in car to any meaningful degree, I would no longer be able to actuate it by simply extending my index finger, as I am now. My conjecture is that MB prioritizes keeping hands on the wheel and presumes, in their unique cultural approach, that everyone will eventually learn the superiority of their design. If we are talking about cars, they have a fairly good track record....



