Searched the browser (js in the first place, but if there is something similar in flash/flex is also interesting) xml editor, the code that parses the xsd, it configures the editor (perhaps as on-the-fly when you download, you may initially installed/configured/compiled for the specified schema). The edit itself should not look like the xml editing code in a text editor, and there is some visualization of this edit, which is set taking into account the semantics of the edited content.
I.e. the result of user experience with the editor xml code that conforms to the xsd schema, but looks editing easy and intuitive from the point of view of the user.
For example, you can see one of the demos
Why can't you take this project, it is not open source, source (no possibility to correct some points), a license is not very understood, but at first glance not what you want (tighter cms'ku it is not embedded).
If the main topic of anything I can not tell, please advise a place on the Internet where you can chat with js developers. Any live forum where there are people who are in the subject. It will be interesting to ask questions about possible architectures of editors.