Multiple synchronized CKEditor instances on the same page?

Multiple synchronized CKEditor instances on the same page?

I'm working on a document-editing application using CKEditor, where the
user can open multiple documents side-by-side in a pair of editor
instances.
Most of the time, the user will be editing two different documents, but
it's also possible that the two editor instances might contain different
views of the same document. That makes things tricky, since I'd like to
changes in one editor instance to be immediately reflected in the other
instance.
Without hacking the CKEditor core, is something like that possible?
If not, would it be possible to write a plugin that would provide that
kind of functionality?
What about if I was willing to get into the core code and hack around a
bit? How difficult would it be?