Perhaps the solution then is to identify every individual who chose to keep chat history off despite awareness of the litigation hold (particularly those where

Perhaps the solution then is to identify every individual who chose to keep chat history off despite awareness of the litigation hold (particularly those where evidence exists here showing it was an intentional choice), charge them with contempt of court, and put them in jail for a year or so. It's a crime, you can get jail time for it, and if you do it enough times, people will pay attention to it.