At The New York Times we use Scoop, a homegrown CMS written in Java. Like WordPress, it uses TinyMCE for editing the article text. This editor is only for modifying the actual text content of the article. Rich content is either edited in a separate pane or in one-off CMSes.
I’m currently working on a team to create a next-generation editor for Scoop, built on top of ProseMirror, an alternative document model editor with customizable schemas, which will replace our TinyMCE instance. Let’s discuss what (and how horrible) contenteditable is, different library approaches to it, and whether ProseMirror could be useful to WordPress.