Fascinating idea.

Is it for the drive itself or to say you did it in an X5? I'm not judging, just asking. Both perspectives are valid depending on your motivation.

Frankly, if you are appropriately prepared ... and ready to film or photo-essay your adventure ... you might even get sponsorship from BMW. Or they would tell you quietly to choose another vehicle. That would be the litmus test for me.

If you are dead set on trying, ask BMW to put their money where their mouth is vis a vis this video:
BMW X5 and X6 off-road driving videos

Net cost alternative: you could take the $20,000 in inevitable damage/depreciation to the X5 and buy an F250 in Bellingham before crossing the border and then sell it on the way back down. Might cost a few thousand overall. Probably less than the inevitable damage to a stock X5. Just like buying/selling a used VW van to tour Europe.

Anything is possible, but I'm fairly confident a stock X5 just isn't the vehicle of choice (normally) for anything north of Whistler. The urban suspension and lack of a true 4x4 immediately come to the top of the list.

Just to clarify what may be required, google "off road BMW X5" and witness the carnage.

Best of luck either way and keep us posted. If you go, you re going to learn things worth sharing and we'll be grateful for the insights and information.

Ian