When click-idetifying a feature having the pop-up window it would be efficient to be able to drill directly down to a related record and edit its values using the edit value function. Also it should be possible to add/delete related records. In addition the related table should have ability to store attachments along with other attributes. ArcGIS Diagrammer should support building the data model for this, i.e. a feature class with a related table where each record in the related table can have other attributes than just the attachments.