It would be nice to add a system setting similar to the BorrowerMandatoryField for the patron form to mark fields important. This would give a visual clue for fields that should be filled in but are not necessarily required.
This would be very helpful for libraries that would like to reduce the number of mistakes when registering without making a field mandatory. For example, our consortium does not have Date of Birth as a required field, but our specific library requires the birthday for accounts. Often, if a staff member makes a mistake when typing the birth date, or enters it into the wrong field. I am imagining something similar to how the MARC bib frameworks allow you to mark a field as important or mandatory, and give you an error message if you didn't fill it out, but allow you to save if you choose to.