I'm not exactly sure I understand the use-case, but as far as the example used in the article, shell-command-on-region accomplishes the same kind of thing. Why not leave the "generation code" as a comment in your file the same way cog does?
Using your emacs-command would defeat that purpose, because you would need to search the region at every run and re-execute it manually again and again and again. And you would need to documentate the command anyway, because nobody can remember all those regions. So why not automate this task then?