First let me mention a strategy which really does avoid the problem: Start at the Aiguille du Midi, climb up the Three Mont Blancs route, and then descend the same way.
(Tour 151 in Ski de Randonee Haute Savoie Mont Blanc, by Francois Labande (Editions Olizane))
But descending the North side of Mont Maudit—often not in condition for skiing). Anyway the Toponeige guidebook shows a rating of 4.3 and the Olizane guidebook says “Difficile” / D+ which I think fits my words of “pretty hard”.
Regarding the idea of starting by descending the Glacier Rond or Cosmiques Couloir:
* Both are rated 5.1 E3 in the Toponeige guidebook.
* G Rond is “tres difficile -” and Cosmiques is rated “difficile plus” in the Olizane guidebook.
I’d say those ratings fit my words of “pretty hard”.
Even so I’m not getting how that approach solves the whole problem, since the report from skiers who were on the scene as it was happening said:
“The Glacier Rond had calved and produced an absolutely massive catastrophic avalanche”.
And at least one famous skier died in an avalanche while descending the G Rond a few years ago.
I note also that the author of the report said that later on their descent his party did ski down the Bossons, but says they still had to first cross the “death zone” again in order to reach their descent route.
(Also by April it is not unusual for the lower part of Bossons descent to lose snow, and to find ski bases hitting lots of thinly-buried rocks before getting down to Chalet Cerro and the wide hiking trail.)
How about pointing us to a trip report by somebody who actually climbed Mont Blanc that way?
Ken