Just for Info,
what I have done for my client is a flexible field where they create the charts, accordions, etc.
Then I added a shortcode that gets all flexible fields created for the post and inserts a span or div with a specific ID.
And then via jQuery I replace the flexible fields from the bottom of the content to the main text. If no shortcode is added the content stays at the bottom (as annexes).
It works great but it is not optimal as I have not found a way to disable already inserted fields in the tinymce menu.
It would be nice to have that kind of functionality but better integrated.
Thanks
