Setting the wrong QNH, being given the wrong QNH or not setting QNH at all will always be a threat, especially to NPA but even to a precision approach. Even with a glide slope you could have a decision height below the runway elevation, which would only leave the radalt, assuming you have one, to save you from a surprise no-flare landing.
With nothing to cross check against, perhaps the easiest solution is for the pilot to read the QNH with the landing clearance if not visual, giving the tower controller a final chance to catch an error.