Perhaps Mercedes should wait and see as the 5-series GT (a similar concept) goes down in flames sales wise. This sort of low minivan design without sliding doors does not appeal to anyone. Does anyone remember the Chrysler Pacifica? Of course not because no one drives one. They even got Celine Dion to try and advertise those six seat faux-minivans and even that didn't work. Do you know how much junk she sold in her Celine Dion Shop when she was in Vegas? The woman could hock up a hairball and people would buy it.
That is the other problem with these vehicles--they try to sell them with six seats. If a family wants a frump mobile they are going to want the full seven seats even if they dont use them. And ask any mother if they would rather have electric sliding doors or regular hinged doors on their family carry all and 9 times out of ten they will cry for sliding doors. It makes it easier to grab junior before he throws his juice box at his little sister.
So come on Mercedes. Give it up. This sort of design has not, does not and will not work unless you add electric sliding doors. But we all know no one wants to spend $60,000 on a really fancy minivan. If that worked Range Rover would already be selling a 4 wheel drive version by now.