I don't think you are going to get a definitive answer to your dilemma. Would it be possible to try an aftermarket hitch and monitor it for your use case? Or would it be an immediate catastrophic failure? Are they expensive? OE hitches run anywhere from a few hundred to a grand. I have no experience with anything but the OE, and even that ends at removing/installing it. But I am interested in any info of OE vs AM as a matter of curiosity. Sorry for not having your requested data points hopefully someone else does.

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2005 X5 4.4i Build 04/05 Maintenance/Build Log
Nav, Pano, Sport (Purchased 06/14 w/ 109,000 miles) (Sold 8/15 w/121,000 miles)

2006 X5 4.8is Build 11/05 Maintenance/Build Log
Nav, DSP, Pano, Running Boards, OEM Tow Hitch, Cold Weather Pckg (Purchased 08/15 w/ 90,500 miles)

2010 X5 35d Build 02/10
Nav, HiFi, 6 DVD, Sports Pckg, Cold Weather Pckg, HUD, CAS, Running Boards, Leather Dash, PDC, Pano (Purchased 03/17 w/ 136,120 miles)