Has anyone managed to get the above working?
It seems I need to add "+body[style]" as a valid_children element, but our site doesnt have a tinymce.inc to add it to.
At the moment, I have added [style] type into the extendedvalidelements and it keeps the style. But comments out the actual style on the page.
I'm curious on why you want to add a style-element through TinyMCE?
But to allow for elements and access other init options of TinyMCE you need to add a plugin as descibed here.