There's an idea in software that's a bit like the corollary of Chekhov's gun. Chekhov's gun is about not presaging jarring story elements that will never come to pass. But it's nearly as jarring to leave important story arcs as complete surprises until the end. Producing the gun moments before the curtain goes down would be quite a WTF. We didn't know that was a possibility. That's a niche that some people occupy, but it is a niche.

Introducing things early fights with Locality of Reference, but when we're talking about things of deep, dramatic importance (like an attempted murder, or a reaper process) it's important to introduce that "character" early in the story so that people know that it exists. Failing to do so is a form of deus ex machina and we only appreciate that in very small doses.

So framed that way, I don't see a problem with having to start a killswitch while you're spinning everything up. It's there, people can see it, and know to ask questions about it.