This is the easy path.
One also has to consider the developers who will wrap existing and well-behaved completion-based apis. Do we really want their code to be riddled with "unsafe" calls, when they do nothing wrong, and they have no way to get rid of them expect writing the convenience wrappers I just described, possibly in a wrong way ?
Unsafety-in-your-face can just be pedantic without benefits, and even have plain bad consequences. I suggest an open mind.