It would be great if, after you've killed a NPC, there was a small chance that a member of its family would come after you:
Paul Shepard: You killed John Shepard at Sol! He was my father! Now I will kill you!
OR
Micky Tricky : You killed John Shepard at Sol! He owed me money! You owe me your life!
OR, even:
Jenny Shepard: You killed John Shepard at Sol! He was my husband! He was also a lying, cheating scumbag and thanks to you I get the house, the dog and his Viper MKIV too!! I've transferred credits into your account as thanks!!!
Why? Why not? NPCs have feelings too
, at the moment they are fodder to be destroyed, interdicted or ignored. Let's give some of them feelings and motives. 
Paul Shepard: You killed John Shepard at Sol! He was my father! Now I will kill you!
OR
Micky Tricky : You killed John Shepard at Sol! He owed me money! You owe me your life!
OR, even:
Jenny Shepard: You killed John Shepard at Sol! He was my husband! He was also a lying, cheating scumbag and thanks to you I get the house, the dog and his Viper MKIV too!! I've transferred credits into your account as thanks!!!
Why? Why not? NPCs have feelings too