Back to basics; why do we need a video recording of the flight deck?
I would fully support such a move, principally to replace those cabin / flt deck communications lost due to the locked door policy; so give the flt attendants a monitor. Do not cite security, if the hijacker is on the aircraft then its too late – its like photographing / finger printing everyone so that after the event you will know who did it and who to blame.
For safety reasons? What more could a video of the crew’s actions give accident investigators? Some insight to the crew’s interaction or haste? Possibly, but little more than that which is already available from the CVR and the latest, extensive FDR requirements; the greatest data deficiency is in the information displayed on CRTs (EFIS, ECAIS, FMS).
An internal recording of each CRT display is viable; the military have been doing this for decades (WIWOL). This information together with sensor data and the FDR would enable a much-improved reconstruction of the state of the aircraft. Again, do not cite lack of recording space, how many film video/games are already stored on board.
What the industry would still be missing is the reasons why the crew did something. If the answers cannot be determined from CRT (system video) and enhanced CVR/FDR recording, then we will have to wait until brain scans and memory dumps are available on the flight deck.