Obviously you are looking for a car that is genuinely capable of towing the caravan, But like JCLoughie I strongly advise you to consider if you really need an SUV or 4x4.
Look at the number of hours you drive with and without the caravan in tow. then consider if you are only doing 10% towing, why compromise your solo driving bu having a less efficient and probably less comfortable car just becasue you tow for a few hours? It make more sense to look at a capable comfortable car, and compromise for the towing hours.
In reality very few caravanners actually ever need to use the 4x4 capabilities, normal two wheel drive is usually more than sufficient.
The 85% is for guidance only, it does not take into account the improved technical capability of modern vehicles into consideration, so its is not a magic bullet that makes outfits more towable or safer. I'm not suggesting you should ignore the principle of keeping the trailer lighter than the tow vehicle, its just something of a sledge hammer to crack a nut.
The advice (For what its worth) does go on to suggest that experienced caravanners might consider a towing ratio of up to 100%.
In all towing activities it relies on eth driver being careful and ensuring the vehicles are in good condition, and driving in accordance with the prevailing conditions.
Might I suggest hanging on to the BMW, and trying it. If you don't like it then consider changing.