I work in healthcare and by far the biggest production issues we've ever run into are people who run Excel spreadsheets through our file processing where the leading zero's have been removed from patient identifiers because that's Excel's default behavior and you CANNOT TURN IT OFF! EDIT: I have no idea who downvoted my post because what I said is 100% true. We have to tell customers to stop opening CSVs in Excel and…
IME numeric identifiers are just asking for trouble. Some systems are sensitive to leading zeros, some systems will zero-pad, loses zero-padding, etc. Worked with a client once with references to the same entity scattered across two databases, one of which zero-padded the identifiers and the other didn't. Oy vey.
That's a failure of the system if it can't be told to not interpret the data. However you're saying the world is as it is; can't argue.