Why not add a VHF compact radio? And a lock. And a signal flare. As nice as the idea of making a repair on the spot might be, you might possibly have to lock the bike to something solid and leave by other means, or call for help. If your bike is disabled, the most important part of the travel package is you. Are you equipped to deal with the threat of hypothermia?

The isolation and harshness of the route and weather you describe would give a reasonable person pause before riding under extremely adverse winter conditions. I am assuming this is not some form of emergency. Cycling is fun and commuting can be too, but there are times and places when it isn't at all worthwhile.