If there is concern over misuse then the information could always be held 'in escrow' by a trusted 3rd party and only released on formal written request from AAIB/NTSB/BEA or equivalents.
Is that not now the case with OFDM data? FDR/CVR would just be an extension of that. Introducing & applying legal constraints that are contractual should not be beyond the whit of man; unions or not. Video would surely require hugely more bandwidth. That's beyond my knowledge. Should any manager be identified as abusing the system they would not only be fired, but end up in court under heavy financial & penal threat. Are FAA/ EASA/Boeing/Airbus even discussing this? Surely an airline could invest in this on its own and take the initiative. It does not need legislation. ACARS was a customer option and look how many have that. When the airlines e.g. Qantas who could see just what their A380 was doing when its engine blew up, decided to invest in that technology you wonder why they don't go further and include FDR/CVR. Mind you that would need cooperation of the manufacturer. But surely the technology to achieve this would be simplistic compared to FBW and all the transmitted systems data, and the manufacturers invested zquillions in that.