With Helios the CC did get into the flight deck, but no one knows when they got there, and so what their options were. If, however, as investigators are commanded, your job is to prevent repetitions of what happened rather than explain exactly what did, you might recommend giving up the locked door on the assumption it was an obstacle to reviving the pilots. They didn't.
IIRC this was a concern of ALPA's when the doors were first mooted. It is still very difficult to get "normal" safety to do "joined up government" with anti-crazy safety. Which is more probable, an emergency like Helios or another 9/11? Answers on a postcard.