This.The only way to do it is to give players more rewards for playing open and in the same moment create an really good crime and punishment system.



The entire idea behind power play is players versus players, each trying to push their Power's objectives. It doesn't really mean that much if no one is there to object to what it is you're trying to do. And it doesn't really mean much if you aren't able to stop other players from encroaching on your power's territory.
More and better rewards for playing in open is the best way to encourage playing in open.
I personally don't really care for people who go around in murder boats just looking for someone to blow up for laughs. C&P has to have some kind of incentive to say "This kind of behavior is acceptable but this kind is not."
A good example of negative reinforcement to stop people from behaving badly is that if you commit crimes you end up on a prison ship 10,000 light years from you where you were and you have to wait for your ship to be sent to you so that you can come back home.
A nice thing to add would be you in front of a blackboard and you have to type 500 times "I won't do that stuff again" while you wait for your ship to arrive. And it won't arrive until you've done it 500 times.

Unfortunately, I know this sort of thing will never be implemented. Expect a number of players to stay in Solo.