I am likewise planning a trip to Alaska. I was originally thinking it would be a solo trip, but my wife now says her only reservation was the Dalton and she is fine going to Anchorage and hanging out there a few days.
When planning a solo trip, my two options were:
1. Buy a GS 1200 or maybe 800, but I don't trust BMW reliability for a trip that long. And these are costly options.
2. Buy a KLR650. Definitely give up comfort, but little doubt that the baby Kaw will get me there and back. And you can't beat $6,500 for a new bike! I could outfit it with the sales tax I would pay on a GS1200. After test riding a KLR this past summer, this was my preferred solo option.
Now that the longest part will be ridden two-up, I am looking at these options:
1. Ride my LT to Anchorage and rent a KLR there for the Dalton segment. This is my current leading option.
2. Buy a GS1200 and add RDL seat and such to make it a reasonably comfortable two-up traveling mount. This is a pricey option and I barely can afford the time and money to keep one BMW road worthy. Two of them would be way too costly in both time and money.
Having ridden the haul road in a tour bus, I would not even think of riding it on my LT. Doing so is certainly possible, but would not be fun and likely would reduce its value by at least $1,000 or more due to plastic damage and extra wear on nearly every part of the bike, but wheels and brakes in particular.
I can rent a KLR for about $120/day which is $720 for the required 6 day rental. Add in the "north of the circle" surcharge of $500 and you still are paying out less than the value you would lose by beating up your LT. And the KLR would make the ride fun, rather than a chore.
So, unless I can think of a better option, I likely will ride to Anchorage with my wife on our LT. She will enjoy six days there on her own while I satisfy my crazy side riding to Deadhorse on a light and responsive KLR that thrives on a gravel road.