No, I'm not missing the point. I understand that there are other solutions. However, my post was made to point out that one of your "other ways" was actually "the same exact way."
To recap, your alternative to having an uberpowerful quest giver was to have uberpowerful bounty hunters.
That's still just bullying the players into compliance via uberpowerful NPCs. As such, it's not an alternative at all.
To recap: The OP wanted to have an NPC give the PC's quests, without the PC's killing the quest giver. To solve that, she was using an uberpowerful NPC as the quest giver.
I suggested using the campaign world, rather than the quest giver NPC's power level, as the control factor to prevent the PC's from killing the quest giver for no real reason. For example, law enforcement or friends of the NPC quest giver, whether that's a peasant or a bureaucrat or merchant or whoever, might not like the PC's acting as murderers and might come after them.
You interpret that as meaning I would send uberpowerful NPC's to kill the PC's, and therefore that I still use uberpowerful NPC's as my control factor.
Which is where you misunderstood.
(a) The deterrent is the concept of a reactive game world, not a particular NPC or group of NPC's. Not the details of what might happen to the PC's, but the concept that something might or probably will happen. Something campaign driven . . . like the people who are selling the items on consignment at the magic shop being pissed off if the PC's kill the owner (low level) and loot the stuff. I don't have or need the details on who all those people are, it's just a logical concept that's a deterrent.
(b) There's no need for a bounty hunter to be uberpowerful anyhow. Slipping poison in somebody's beer or blocking the exit to an inn room and starting a fire doesn't require a high level NPC. The last time an NPC sent killers after PC's IMC, they were neither more powerful nor more numerous, just clever -- attacking when the PC's were split into three groups (one group having chased after a red herring the NPC's set up) and some of them were drunk. The fight turned out to be a draw, with the killers escaping and no PC's slain. And of course there are other deterrents besides trying to kill the PC's, such as merchants refusing to deal with you, demons trying to recruit you, etc.