I typically have rhythmbox running on the first workspace, to keep it out of the way. I used to have it minimised (before gnome 3), and would still prefer that (bu that's another matter entirely).

When rhythmbox crashes (sadly common) or I accidentally close / move it (not all that common, but still annoying), I can no longer have rhythmbox on the first workspace[*], which is important because:
 - it's out of the way
 - it's the only consistent workspace (there's no such thing as always having an app on the "last" workspace)

To assist with this, I would like a way to reorder workspaces. So after a crash, I would open rhythmbox on the last workspace, then move that to be the new first workspace. For example, perhaps holding down "alt" while dragging the workspace's icon in the overview mode would allow me to drag the workspace (instead of the window) to reorder it.

[*] I tried once, by shuffling windows individially between workspaces. But if you move the last window off workspace n without first moving at least one window from workspace n-1 onto it, you immediately lose workspace n. Pretty infuriating, although I understand why it happens.