Has anyone approached Cosmique Hut by this way, instead of the usual method of taking the cable car to Aiguille de Midi? It seems to me this a 'cheat', taking all the expedition/approach aspect away from a climb of Mont Blanc. (Similarly, taking a ride to Nid D'aigle on the Gouter route!) So, my idea is to spend 2 days walking from starting point Chamonix itself, up the Mer de Glace, stay at Requin Hut. Day 2, walk/climb up Vallee Blanche to Cosmique, spend night 2 there. It seems to me this would help take care of acclimatization too, being a very slow schedule (only 6km per day), reaching almost 4,000m over 2 days. My biggest concern, though, is the terrain, having heard much about the crevasses there, and nowhere can I find reference to anybody having done this (there must be a good reason!). But it is a hugely popular ski route, so how dangerous can this vallee be? A walker can surely avoid crevasses easier than a skier? So, main question is, has anybody walked up the Vallee Blanche to Cosmique, or heard of anyone doing this? Secondly, is it possible in May?
That said, I imagine it's doable if you're willing to suffer. From what I saw of it, it was heavily crevassed and broken up last July. It would be gnarly to try to get through. The fact is, Mont Blanc is not an "expedition" peak. You can't camp above a certain height (if at all), and even bivying is somewhat discouraged. There's just too much traffic.
My advice would be just to take the lift, enjoy the climb, and use the week you saved trudging to climb other cool stuff in the area. Not having to slog through an approach is kind of the point in Chamonix.
I have walked this route a couple of times as a training and acclimatisation route. The worst of the seracs/crevasses are on the part of the glacier below the Requin hut. They are bypassed because you leave the glacier for the route to the requin and you exit the Requin above the seracs. Early season, I did it in June one year, there may be a lot of snow on the route and snow shoes are necessary. If you went in May I guess you already found this out.