Just test your “Merge with the menu tree” pretty cool, thanks.

The only two things that I don't like is:
1— You cannot Name that tree (like the menu tree), it will be great to be able to name it e.g “Articles” or “Content” to further clarify for the Viewer what exactly they are looking at.

2— You should have the possibility to keep the folder close for the Content source and the same choice (close/open) for the menu tree. I said this because, this “Merge” option will not look good open in most of case as you can have hundreds of articles in the content source. It is rare that menu have many elements.

In my case, it will not work for that reason, because many articles will be added to the site and will make an really long (to long) Content tree because I have no way to choose keep the Menu tree open and the content tree close because the setting are situated in the General configuration.