Unfortunately, that feature is not built-in to wxPython. The closest thing that I am aware of is "dockable" pains in the AUI framework. I would recommend looking at that, especially the pure Python version of AUI that is in wx.lib.agw.aui. You can see an example of its use in the wxPython demo.
I am thinking that you might be able to use a dock from that inside your ribbon control and add docked panes to it that can then be moved around. I'm not sure if this will work the way you expect, but it's the best available without creating something new. Otherwise you will have to create a custom widget.