Copy-pasting contents from a webpage that contains images links the images by
default (I object to this behavior, but I assume it is already like that for a
reason?), and the user cannot easily figure out how to "save" the images with
the document.

The only way I have been told is to use the edit menu and use the "Links..."
item. I would like that to be availabe in a popup menu when clicking on images
and/or in the image toolbar.

If the user does not know about that, he will just assume his images are "saved"
and will have very bad surprises. Here are the consequences of the current "link
images" default behavior:
* Everytime you load that document, if the images were on the Internet, you will
need an internet connection
* Even if you have a fast 3mbits internet connection, it will make your computer
hang for a LONG time loading those images.
* Moving through the pages of a document makes you lag in a terrible way (images
are loaded one at a time (or so it seems!)
* Deleting those images is painful because, once again, you lag while doing that.
* If you copy-paste contents from a local HTML page that has images, and delete
the page/images OR move them, the images will be broken inside the ODT file and
you will have no way of accessing them.