I might be near some sort of "super equation editor" - after pasting applet of Dragmath to the top of my prototype editor and changing the target of Dragmath Insert button to textarea of prototype plugin things look really sweet...
I set meta.php to use two different asciimathml versions - full fallback version when editing is off and short version without asciisvg and latexml code when editing is on to avoid conflicts between tinymce and asviisvg in IE. Using modified plugin Preview I can preview the content of editor textarea with link to full asciimathml code in plugin itself and in prototype plugin editable equation can be previewed with mimetex or some other code...
Fallback of asciimathml works pretty well also in IE without Mathplayer - we still need some solution to asciisvg. Chrome has some odd problem with Dragmath and inserting mathexpression and image maps - Opera, Safari, IE and Firefox seem to work well...
