>...would it not be possible to treat the tape as the CVR/FDR are treated today ie. restricted access?
Restricted to whom? Far too many CVR/FDR information has found its way into the open media to be disected by uneducated and uninformed "reporters."
There is nothing additional to be gained from video that can not be deciphered already with current CVR/FDR capabilities. Take the Egypt Air mishap for example. Mount a camera behind the pilots' seats and watch the video (if it survives). Was the co-pilot pushing the yoke or merely preventing yoke from moving aft? You don't know from the video and never will. OTOH, capture yoke pressures and movements on FDR and you'll know if the yoke moved first and the pilot reacted or the pilot pushed the yoke and the controls reacted.
From this former mishap investigator's point of view, I'd much prefer improving CVR/FDR information rather than wasting the time/money on a cockpit video system of limited value.
*NO CARRIER* -- A Naval Aviator's worst nightmare!