Though I already have an aftermarket hitch installed on my '01 X5, i've been following all the hitch, wiring, and module threads concerning the 2000-2006 E53.
I was going to make my cobbled-together 4-way wiring into a 7-way, so I could tow my 4x8 camping trailer (with electric brakes, because it's heavy, at 2225 lbs), but since I quit camping (and already have 2 trucks with hitches and 7-ways), I never did anything about it. The X5 could still tow it or my 5x10 utility trailer (never used since I got it 4 years ago), using the 4-way without brakes, which would be OK since the X5 has good brakes already.
The hitch I have on the X5 is the Draw-Tite 75492, which is the same design, as far as I can tell, as the Curt 13162,
which the Curt Numerical Trailer Hitches chart
https://assets.curtmfg.com/webfiles/...Hitches_19.pdf shows superceded the 13070.
I never found the vaunted S019 hitch anywhere, to see how it compares to the 13070, or the current 13162 model.
Many have complained that the underside bracing bar, on both the Draw-Tite 75492 and Curt 13162, isn't needed nor looks good, but it is there for a reason...to help support the weight of the trailer tongue better. I also view it as a plus, because it will contact the ground first (instead of the lower rear valance/bumper cover) and force the X5 rear to rise up & over an obstacle (handy if crossing a ditch or even a speed bump, if your ride height is low).
But, anyway, every X5 should have a hitch, because what's a SAV for anyway?