There is a lot to explore on the side of Smalltalk machines, Oberon, Lisp Machines of old. As a developer, live programming language based environments is my kind of thing.
I was a big fan of the QNX demo floppy (1.44MB OS with browser), but that didn't lead to me using it on the desktop. http://toastytech.com/guis/qnxdemo.html
There might be room for something new and different that runs on it's own VM (like Smalltalk) and can use libraries on the host to get things that do not make sense re-implementing, like a web browser. If it gains sufficient traction, the work to move it to a more stripped down environment would be clearly worth it.