I have my own uilt CMS for my sites which I have always used InnovaStudio Live Editor or CKEditor to allow users to edit the content of their pages.
I have been looking for a Drag and Drop WYSIWYG Editor to replace those but I can't find anything online.
It will probably have similar functionality to the editor in: [url removed, login to view]
Where you can drag elements into the page in certain positions - and all those similar things, e.g. Title, text, Text with image - images galleries, etc etc and possibly more or that it could be extended.
Maybe there is something out there which already has that functionality you have used before or can develop something similar.