I finally got around to reading this. You're right, there is some evidence that willpower-poor individuals can be easily trained to do better (assuming they can actually implement for a long period of time some habit which involves self-regulation). Amusingly, there's also evidence that consuming more glucose also helps ward off ego depletion.

My detailed response is here: http://graehl.posterous.com/evidence-that-self-control-can-be-trained-lik