Not getting caught in the pack-ice!
Sounds interesting.I have no specific knowledge of the route but would offer a couple of comments.
1) It is a very long way and I wonder if a sailboat could make the distance in one season even if the ice conditions were agreeable. You would have to make it to Vancouver or Japan before the fall storms hit. At best you would be rushing the whole time.
2) You would have to find out if there are bailout ports along the way where you could get hauled if you got stuck along the way.I know there is commercial traffic along the coast of Siberia but I don''t know what cranes or marine railroads there might be. Also I don''t know if I would want to leave my boat in Siberia for the winter (or stay with it for that matter!)
3) I was cruising in Newfoundland this summer and talked to a couple who had sailed the coast of Labrador and were hoping to go to Greenland. They indicated that charts were marginal (at least they were not in Russian)and that ice was frequently a concern even though it was technically an ice free time. They were considering replacing their Mason 43 with a steel boat for more security in ice.