A broad conspiracy to defraud its customers out of hundreds(?) of millions of dollars as well as governments, and you just want the kingpin? Is it because the coders can only do what they are told? So would you say that the good and true engineering of those vehicles was also due to the CEO?
We don't let larcenists off the hook due to size of their tax return, we don't let the get-away driver get-away based on high unemployment rates. The CEO may have commanded this done, but the coders surely pulled the trigger. For years.
As for the plan your suggesting where the execs should be forced to return bonuses, I am sure the board of directors would love that. Even though they could very well have been involved. And the shareholders, they should get those bonuses back even though the shareholders choose the board of directors have enjoyed higher returns based on this likely criminal activity.
I would like to submit the idea that the customers are the victims here and the ones that should be compensated, and that VW the company should be the one to do that. After that, persecute the CEO if it makes you feel better.