I have found a need for this one a couple of times too.
After version 1.0, which we are focusing on tasks management, document management is the current-top-candidate for improving. So this feature will probably make it soon (at least the first paragraph).
Note that you can have the same document in more than on Workspace. So, when you batch-move a document, it will probably be similar to what you see when you move a single document (you chose several workspaces where you can access the same copy). The 'new' feature in that matter would be: 'create a copy of this document'.