Currently, the Hub conformance statement specifies which events are supported. However, that is not so nice for a Hub, if event customization is a feature. So can’t we have an Hub just pass on custom events regardless from if the EMR that hosts the Hub listens to those events?

Consider integration between an ImageViewer and Dictation system with EMR/RIS as hub.  The EMR/RIS should propagate any events it does not recognize, right?