It sounds like you already have all the information you need about camping, so you know that it's possible but not risk-free, but you're the only one who can make that final decision. (I trust you know why camping's officially banned).
What you really need to think about (when you get there) is if the weather's up to it. This route's only feasible if both the forecast and the snow are perfect.
I would question your decision to leave at sunrise. This is a 6-7 hour route, and the same in descent if you're doing it in nasty, soggy afternoon snow. I would leave around 1am and aim to be back for lunchtime. In any case, my preference would be to descend via the Gouter ridge - no uphills to contend with, and several huts where you can rest if necessary.
BTW, there are no lockers in the upper station, but you can stay in there if the weather's bad and there's no room in Cosmiques hut (officially it's not generally allowed).