FYI, I've gone past this point in my own playground, to the point of having a working tabbed editor implementation.  It's not that much further actually. Here are the next steps:

1. Change so that Container is passed to Components on creation, rather than Component creating its own container.

2. Change statusbar so that it's in control of what is displayed, and EditorWindow just pings it to update itself; statusbar calls into EditorWindow and chooses what info to get.

3. Change so that container decides how to display title, EditorWindow just says title has changed. Add saved/dirty status info to Container.

4. Create Container subclass TabbedContainer using the separate uitabs.py widget I put together. Manages the tabs and switching in different content as tabs are switched. Altogether < 100 lines of code.

5. Create Container subclass ProxyContainer, representing what's managed by a single tab. Just passes things off to TabbedContainer. < 50 lines of code.

6. Change FileList to created a TabbedContainer and then ProxyContainers for each  shell/editor added.