No, because if it can be opened by a flight attendant, it can be opened by a flight attendant with a hijacker's knife at her throat.
Pilots should be subject to prison sentences for stuff like what these two did. That's more likely than anything else to put a stop to this sort of thing.
How about a flight attendant asking for access and if no confirmation from the flight crew and an OK from air traffic control, a small door within the cockpit door could open so the Flight attendant could at least see inside and talk to the flight crew.