Plenty comments on tow-cars, but one thing that seems to be missed is rear suspension. One thing to consider is the rear springs on what is basically a conventional saloon or estate car.
I tow with a 2001 Audi 2.5TDI quattro avant. It has sports suspension, so sits a little lower than conventional SE variants, but the key thing is the springs are stiffer. I've replaced the springs on my Audi a couple of times, as coil springs invariable break every 4-5 years. Combination of road salt (typical Scottish winter) plus the stress towing probably puts on the suspension components. This is hauling an unbraked 750kg trailer. There's still quite a bit of weight on the trailer nose, so it's not unusual to watch the car dip once you hook up.
One thing to consider, but I'm sure the BMW will be fine. Having 4x4 capability is useful, but it's by no means essential. 95% of the time you're not towing, so it's all about what suits you.
Is that with or without VAT?