It would be nice to draw attention and require a note field if a library is designated as a delivery option for holds. To recreate: 1. Be sure OpacHoldNotes is set to allow. 2. Create a library called "Interoffice Delivery". 3. Sign into the OPAC and place a book on hold. 4. Select the pickup library as "Interoffice Delivery" No attention is drawn to the note field and it is not possible to make it required. In this scenario requiring the note field be filled out with address information would be useful. This would be separate from the Housebound module, because delivery would only occur if requested by selecting Interoffice Delivery as a pick-up location.
As a workaround, I think you could achieve this with some JS in OpacUserJS.