Hi Sarah, great diagram! Very helpful I think to see both the possibilities and the relationships.
I suggest to add Akvo RSR (really simple reporting) to the scheme. Using a generic link to an xml file, one can add or update project data in the Akvo RSR project editor and create a new IATI file which is hosted on the RSR server and immediately availed through the generic link.
More information on how this works is captured here: http://rsrsupport.akvo.org/article/show/how-can-i-publish-to-iati.