It’s taken almost two years, but Mercedes-Benz has finally given its slow-selling R-class MPV the option of five or seven seats and rear-wheel drive.Previously, Merc’s massive machine was something of a curiosity: it had four-wheel drive but wasn’t an off-roader, and despite its massive size it had room for only six people and not much luggage.Now the R-class will be available with the option of five seats and a whopping boot, in the manner of a conventional estate car, and seven seats (2+3+2). It will also be available as rear-wheel drive only, saving weight and crucially cutting the entry price by around £4000, to start at roughly £36,000. Previously the R-class was more expensive than the more desirable ML off-roader.The existing R-class seat configuration (2+2+2) will also remain, and as before all R-classes can be ordered in either short or long-wheelbases.On top of all this, Mercedes is also introducing a new engine to the range – a 3.0-litre V6 petrol in the R280, which is rear-drive only.That means the R-class range now runs as follows: the R280 CDI (available as either RWD or 4WD), the R320 CDI (4WD only), the R280 (RWD), the R350 (RWD or 4WD), and the R500 (4WD only). And every model can have either five, six or seven seats and come in either a long or short wheelbase. Confused? We certainly are.Mercedes has also given the revised R-class a slight exterior makeover, with new fog lights and what it calls a “highly distinctive bodystyling package at the front and rear”. We’ll let you be the judge of that.