Re: I got me a new tow rig!
The BMW's and other brands of luxury vehicles are very, very strong in structure. The big problem is with the independent rear suspension having limited strength. No unit with CV joints on the back end will meet the strength of a live axle with solid steel axles.
That said, you're okay to pull a single jet ski on a lightweight trailer. Or, pull an ATV on a light trailer. You'd be okay to pull a light aluminum boat.
Otherwise, get yourself a pickup truck to haul all your junk.