You pretty obviously don't want to mess with it frivolously. But if there's something wrong with it, and you have to fix it? That seems better than the alternative where you can't. Note that the right to modify it doesn't imply that you're required to in the absence of any reason to.

Also, if someone wants to kill you in your sleep, they... don't need you to even have a pacemaker. And the security of medical devices is notoriously bad, so if you're worried about that sort of thing, be more worried that the status quo doesn't allow you to fix the existing remotely exploitable wireless security vulnerabilities.