FD/Lom,
My experience (though limited I admit) of the DGAC says that unless you know exactly who you need to talk to there you will not get much help at all!!
In addition to the DGAC though, there is an organisation in France called the FNA Federation National Aeronautique which supports/encourages/promotes GA flying in France, and I suggest trying them, as they may be more user friendly to your friend.
Website
Here
Out of interest, whereabouts is your friend in relation to Bordeaux and where was he flying from? I am very surprised no-one at his aeroclub can help him (mine is very friendly & supportive) with info or help him find a way around the problem, especially as he got to solo stage and no-one noticed any problems.
Regards, SD..
PS, I will ask around at my club next time Im there to see if anyone knows anything about disability exemptions here.