@Johnathan, I think you might be misunderstanding my complete schema so I'll explain it.
It is for building inspections, post-earthquake, using the ATC-20 form. So we start with a feature class (building footprints), and then we have a one-to-many relationship with inspections, now using GlobalID and GUID. Each inspection though can have multiple photos taken in the field, so that is another one-to-many relationship. So it's feature class, to a related table, and the items in that related table can have attachments in another related table. My question is for the photos related to the inspections, which are related back to the building footprints, how does the relationship need to be created? Is it GlobalID (of the inspection) to GUID (of the photo)? In any case I can't create a GUID value for an attachment that hasn't been created yet.
For what it's worth, this setup has worked fine in Collector without any GlobalIDs or GUIDs for a couple of years now.