Pickup trucks and people movers are out of the question, so it must search for more creative answers that still fit under the rubric of “ultimate driving machine.”

Some of these line extensions have been successful, like the X-5 and X-3 sports activity vehicles that managed to maintain their BMW identity at the same time that they incorporate all-wheel-drive and an off-road attitude.

Other new ideas have seemed like a stretch, like the X-6, which blends go-anywhere SUV capability with four-door coupe styling. That combination of features seems less inspired.

The other day, I forked over $40 for a few hours parking and took delivery of a new 550i GT. On sale since December, the GT is another four-door with coupe styling but one that leans more toward the car/crossover side of the spectrum.

The first thing I discovered is that far from being a sleek grand tourer, the GT is a big vehicle. The wheelbase and track are closer that of the top-of-the-line 7 series. Extra size, height, and some unique apparatus in the rear push the GT up to 4,938 lbs, making it nearly 1,000 pounds heavier than a 5 series sedan.

That apparatus is the dual purpose tailgate that is the GT’s raison d’etre. Open the lower gate and it’s a conventional trunk — and a big one at that. Open the rear window glass along with the gate and you have a hatchback with even more room for your stuff. Think of it as the Swiss army knife of luxury cars.

The GT is very clearly a niche vehicle, aimed at that mythical affluent couple that goes shopping for antiques on Madison Avenue or hauls home cases of wine from Napa Valley. Affluent they had better be, for while the base sticker price on my Space Gray Metallic test car was $63,900, an array of options plus a gas guzzler tax pushed the final tab up to $77,025. Even that robust number didn’t provide for seat heaters — required equipment for New England in February — or satellite radio — a luxury to be sure, but an inexpensive (and habit-forming) one.

After putting more than 400 miles on the GT, I was never less than engaged by the car. Sitting in the driver’s seat with all that electronic and mechanical capability at your control, you begin to understand just how seriously the product planners, engineers, and designers of Munich take their vocation. It would take me a week to comprehend all that this car has to offer and to put it to proper use.

I expect admiring comments from my friends when they see me in a BMW, but I got more brickbats than compliments when I showed up in the GT. The dual purpose tailgate upsets the balance of the vehicle and gives it an overstuffed rear end. What this BMW gains in utility, it lacks in curb appeal.

The 550i GT seems like a reach too far. A 5 series sedan — to my mind the essential BMW — provides all the driving pleasure you need for thousands of dollars less. If you really need the GTs hauling capacity, you can always add a used pickup truck to your driveway.