Andrasz,
you stated earlier:
Also not mentioned here previously, the role of those three security personnel on board is not limited to in-flight, they also maintain ramp security during turn-arounds, and they are the ones who actually open/close the cargo doors. Anyone trying to gain access to the avionics bay would have to dodge them. Not saying it cannot be done, but rather unlikely during a short turnaround.
It was reported in the NY Times today that the on board security personal on Egypt Air does all of these checks you mentioned, except in European airports.
NY Times:
Security officials said those procedures would have applied to the EgyptAir plane during short layovers it made at two African airports — in Tunis and the Eritrean capital, Asmara — in the days before the crash. But the procedure is different in Paris because European airports do not permit EgyptAir security officials to search local cleaning workers, a source of disgruntlement among Egyptian officials who feel they are being discriminated against.
This adds a bit of intrigue to the security situation in Paris....
