I have the same issue did you ever get an answer?
I am also trying to transfer attachments to a new feature class in a different gdb (same geometry, different schema)and I have yet to figure out how to get the attachments to go with the geometry, I think it is partly due to the fact that collector calls all of the attachments photo_1.jpg...and partly due to me not knowing how to work with relationship tables as well as I should...
How do you store the photo's? As a blob in the table or as a (hyper-)link to an external source?
I'm trying to achieve the same goal, hopefully we can team up.
Right now as a blob in the table, but I think we might migrate to a hyperlink to an external source.
I see what you mean after having exported the feature layer to a file geodatabase and downloading that. It contains a table having the pictures as blobs amd a column referencing the point and the picture. Can't you just rename the strings in the ATT_NAME field? Seems to be a string only and the globalID is the unique 'name'.
Right now I'm handicapped because my basic license is "Not licensed to edit layers with relationship classes"