Hints towards a recommandation
IMHO, one of the immediate recommandations that should be given :
Publish the best glide speed in typical flaps/landing gear configurations, and train the crew to react to full engine failure.
Because, for sure, let us putting it straight : the handling of the event was less than perfect and that is something that should be improved. I presume some chief pilots are already working at it ...
AAIB doesn't need to know the causes, for that first step.
Yes, it does happen, from time to time ...
Boeing should be able to provide the data ...
Crews need some numbers, some practice, too.
Long overdue ...