How about when they get back to their ship all the wires are sticking out of the panels on the dashboard because the feds were searching it for onion head.
How about - if I so much as think of fitting an interdictor, I am arrested by Thought Police and I'm locked out of the game for 24 hours. And my ship explodes for good measure.
I think they should be sent to the most populous system in the sector, so other players could go there, throw peanuts at their imprisoned holo-mes and yell "dance, griefer, dance!"
Some griefers are just murdering psychopaths, murdering noobs in their first Sidey, on their first trip out of the station, in a FDL or even annaconda. They surely deserve to be severely punished. The more severe the better, I say.
To be frank, doors are open for such a tweak, especially if combined with Karma. Karma might add factor of pushing even more away from system where you got nailed.
However for regular criminal behaviour having you thrown out of system is enough. If it is 4 jumps even then it is enough time for people you attacked to regroup and disperse.