I know; and I definitely support the idea. I think we would get a long way towards this by a throwing the WYSIWYG approach away and using a moded editor.

Text entry mode not allow for layout choices; it would only produce markup and both try to guess what the user is doing (double linebreak = paragraph, f.ex) as well as explicity ask him to mark up his text ("this is a headline"). Text would not appear formatted in entry mode either.

Layout mode would not allow for text or markup entry. Only formatting choices for existing markup can be made here: select a headline, and you can adjust the CSS formatting for that level of headline, or make choices for the specific headline in question (via a classname), or both. <span> tags might be an allowed exception.

Makeshifts last the longest.