Hi,
Great work with your UI mockups Mark, very clean!
There is another UI approach I think we should also investigate. It is not incompatible with your approach and in fact could nicely complement it.
The concept comes from a demonstration I saw of IBuySpy Portal and shares some of the best ideas from dotLRN's portal manager, ETP, and even our current sitemap.
From what I recall, site admins could manage pages as well as mount various modules through a standard "tree" interface. When editing a page, you could add and edit portlets anywhere on the page. A portlet might, say, show site visitors the last 5 news items or top 10 discounted products. You could also add content anywhere on the page in a similar manner.
The demo planted the idea in my mind that an ideal CMS is more than a simple content management system, but rather a site management system. I'm not suggesting we build this for the first phase, but that this could be a guiding vision.
Here's some URLs relating to IBuyPortal:
http://www.cebware.de/download/programs/mobilewebportal/index.htm (the only screenshots I could find, in German)
http://www.asp.net/Default.aspx?tabindex=5&tabid=42
