I stand to be corrected (as usual!) however I believe that the legality of a duty is based on what is planned rather than reality. And, although you will never find a definition of "planned" in this context (even in JARs), it would appear that it refers to the scheduling stage. So if it can be demonstrated that, using historical wind data, say 80% of the time a flight can be completed within the FTL then it is legal to schedule, and any deviations can be accomodated with 'captains discretion'.
So strictly speaking I don't believe there is anything illegal here. However if it is not realistic, enough ASRs should bring attention to it.
Incidentally I don't believe there is a requirement for the augmenting crew to be in the flight deck for take off and landing.