Ray -
I really appreciate the work you put into the reply - exactly what I was looking for. Well, actually, I was looking for a definitive "yes or no" but in reality your answer probably serves me better.
I'd like to think that although it is marketed as a "Sports Activity Vehicle", if the engineers and manufacturer gave it a factory trailer hitch option and a 6,000 towing capacity that they actually mean it (and beefed up the frame and transmission to support that application). That said, I'm scratching my head to recall if the X5 was built new from the ground up or if it simply uses the 5 series frame...I know it won't take me long to get to the bottom of that one.
True, BMW is known for their sports sedans but they're also known for extremely high engineering standards and quality workmanship. I would be dismayed/surprised to find out that in reality the X5 should not tow more than a couple jet-skis.
BTW, my X5 is alpine white and the thought of it pulling a shiny white TM behind it...well, that would be a pretty cool picture. Imagine the looks as I chug like a freight train past the other cars going up the mountain gasping for air (gotta love BMW's VANOS**!). Ok, maybe I'm spending too much time with my 3 year old's train set.
Rick
** VANOS, in case you're wondering, is BMW speak for their steplessly variable valve timing. Breathe baby, breathe!