Allow to display the content of a document like any xobject field

XWikiDocument currently exposes an API to display a field in edit mode or any other mode. However it's not possible to display the content of the document in edit mode.
I recently had this usecase when working on an extension sheet, where the descriptions of some entries are stored as the content of the document: I wanted to allow people to edit this content directly in my extension sheet, and using $doc.display('content', 'edit') is not working since it's not part of my xclass.
A workaround for now is to create a pseudofield in the xclass containing only a {{include reference="AppWithinMinutes.Content"/}}.