The goal would be to go before the breakup happens. As it appears, the sea will thaw before the inland Siberian rivers and marsh (due to colder temps and freshwater) so the heading-west works in that regard. Once anything begins to thaw, we have discontinuous ice which will represent enough of a hazard on it's own. The real question is, can the kraggy parts be either circumnavigated, or be dealt with in another reasonable way? I think it will only be answer by a preliminary trip to AK to experiment with the ice. If the crags are as "small" as Going South's images imply, then it's doable. I think they will be bigger, though, as many of his pictures were not fully frozen areas, which will compact the ice flows more and exacerbate the problem.