It would be great if PerchAPI_ContentImporter can handle locating and updating existing items like PerchAPI_CollectionImporter does.
I have a custom app that uses PerchAPI_ContentImporter that I use for multiple websites. Each website needs content imported from a different third-party source. So I'd normally write a client-specific app to integrate with the main app to import content. Being able to also locate and update items would be extremely useful.
Third-party Perch apps can also make use of these features to offer more integration options for other developers.