I've got no problem with the limiter. Any idiot can kill; it takes ingenuity to find alternative solutions. And if there are situations where Gan's inability to kill is an impediment, well, what's wrong with that? You're not supposed to make things easy for your characters. The more the deck is stacked against them, the more suspenseful the story.
Not to mention that the existence of limiters helps illustrate what a police state the Federation is, using invasive devices to mind-control people.