I realize this is an old article, but I want to comment on it anyways.
I really resonated with your article! Also pretty cool that you wrote your own little proof of concept editor! A comment on that: the way you used it seemed not so different from having several panels open in one of the classical code editors you mentioned. You did not use what is in my mind one of the most powerful affordances of a two dimensional code layout: zooming. I think I’d prefer to have all files / classes / functions in a project laid out in a huge canvas at once. I could then start to build some spatial memory of where things are and how the control flow works on that canvas. Navigation would work by smoothly zooming out panning and zooming in again. Like in a Prezi maybe. Your pair programming buddy will get motion sick in minutes, but I bet the driver seat experience would be great :)