Whats wrong with it??
It wont be a piece of shit, it will be a BMW minivan. They wont call it a minivan becuase there won't be much about minivans like this.
You ever try to haul more than 5 people in an X5?? It won't happen. There's nothing wrong with this. Mercedes builds semi's and holds the major share of that market in europe next to volvo.
I do not like minivan's, but it's not like any of you will buy a bmw minivan to be cool -- you'll buy it becuase it'll be super luxurious, 100 times sportier and better quality than any ford, pontiac, or chrysler minivan, and it will still be a bmw. It's not going to be your typical $26,000 minivan -- I'm sure it'll cost about $45,000 atleast.
I wouldn't buy one for myself -- but I see nothing wrong with the concept.