Provide a means of getting ALL properties of an EWS item so that an item can be copied in full fidelity
Currently there appears to be no way to get a complete copy of an existing item via EWS, whether it be an EmailMessage, MeetingRequest, etc. Any application that need such functionality appears to be impossible to do with EWS. While it's possible to get all known properties (albeit an awful unwieldy solution - https://ewseditor.codeplex.com/SourceControl/latest#EWSEditor/EwsPostExamples/GetItem - AllKnownProperties.xml), this won't work for any custom properties, which means that 3'rd party applications will not function correctly.
Here's a couple of examples of people needing this functionality, presumably you already know of more:
Thank you for the idea! Although we appreciate your time and effort to give us this feedback, this doesn’t align with the general strategic vision of our product – we are focused on adding more capabilities to the REST API, so this is not something on our EWS roadmap right now.
Office Extensibility Team