BMW already tried a V8 diesel in the 7 series sedan. The fuel mileage was much worse than the 3.0L 6 cyl and the power output from the 3.0L is "more than adequate", so they dropped it. This is in their European offerings of course.
What I'd like to see is more small diesels in small cars. i.e. BMW 320d; and more AWD/diesel passenger cars.
My next vehicle is a HZJ79 Landcruiser pickup from Proffitt's.
Unimog U500 with Unicat camper; diesel BMW X5 35d, diesel BJ40 Landcruiser and diesel M37