In reply to ChrisJD:
All valid points.
But please remember, I am being responsible, by asking the question to those that know much more than me. That is the whole point of asking a question to find out the answer and then act on it. Why would I ask the question in the first place unless I wanted answers from more experienced people and planned to listen? The other reason I asked was because Theo asked be to, and he has read the responses. This has helped him form his own views, rather than me just saying, No!
At the time of asking all I knew from the web was that it has been climbed by kids of that age, but had no idea how common this was (it now seems not to be, unless you are French).
PS. If we were to do it, and this now seems very, very, unlikely, the rest of the team (except me) would all have done MB many, many times. Nor would it be his first 4000m peak as he would have had to show to me he was happy on some of the much easier just 4000'ers.