Thank you for all your feedback!

Scott, you really changed my mind! The Dempster it is now! And the ice road!

I have posted the same question also here:
Expedition Portal
X5 on the Dalton Highway in March - am I nuts? - Bimmerfest - BMW Forums

I am currently contacting BMW North America and Germany to see what they think about such a trip.
Depending on BMW's feedback, I might change the vehicle to a Toyota Tacoma or FJ Cruiser.
Once, it is a go, I will let you know and post from the road whereever wifi will be available ;o)

Thanks again for the great feedback!