I would work on making the existing writing clearer before expanding further. There were a number of points where I did not follow you as a casual reader, like with the "circular money pump" and Sen, or things just appeared random, like going from has specific theoretical pitfall to BAD.

Second, if you are going to expand, you may want to address whether all this theory actually predicts much accurately. Beyond saying, yeah, there were these guys Duncan and Black who looked at specific cases--what were those cases?