These guys know what I'm talking about when I mention tearaway windows and customisable easy to use interfaces. Take a look at the example video found here: http://www.kirix.com/labs/wxaui/screenshots.html
Playing around with it briefly using wxPython was reasonably painless and showed how easy it was to accomplish something like this relatively quickly. Unfortunately it also showed up some instabilities in the latest build.
I'm going to have a play around with wxWidgets in C++, see if it has the same issues I experienced with the python wrapper. If that doesn't work I guess I'll start looking at other widget systems.