it would be hard to argue that anyone legitimately invited to the flight deck by him/her isn't then duly authorised to be there.
Exactly. From personal experience I know that some European carriers still leave it to the Captain's discretion and ultimate responsibility. Since 911 I have never asked to go to the FD but, to my surprise, I have on three occasions been invited to the front office during the cruise and then later also for the landing. These were respectable European carriers including one major. Yes, my ATC I/D was checked but basically they didn't know me from Adam. Additionally in some areas outside Europe/USA/Canada things are still much more relaxed. Not with all, but with quite a number of companies. Again, those companies leave it at the Captain's discretion. I have also witnessed friends/girlfriends/family members gain access quite openly on a few occasions.
For sure, the strictest adherence is by British and North American carriers and worldwide major carriers. But my point is that there are more exceptions than many in the industry care to believe. However, not many, if any, who work for these more "liberal" companies, frequent PPRuNe. And those who might, probably will not particularly wish to advertise the fact.
Bottom line for the O/P: probably zero chance with EZS but you might get lucky elsewhere someday
