I very much like this idea.
I think it works well for all sorts of data. As a programmer, I would love to see various documentation written this way. And I would want this to nest the way an outline might, so you can have hidden content inside hidden content, and so on.
I would love it, though, if it could be written much more simply, using some sort of parser that allows for something like:
<<stretch-outline """
General information
+ proof inclusio gloria
+ proof identifying with hearers
+ proof no xn elements
+ proof stuff not in AT
+ proof list OT refs
Themes
+ proof God act outside Israel
+ proof themes opposition
+ proof themes lack of recognition
7.2
+ Stephen's non-response
+ Abraham's call
7.7
+ altered Exodus quote
7.8
+ spiritual circumcision
7.15-16
+ Hebron or Shechem
7.17-20
+ Moses/Jesus parallels
7.37
+ play on Deutoronomy 18.15
""" >>
where each of the + title notations does the same thing you do with <<blurbtext ...>>, and indentation in the document translates to proper nesting in the output. While that doesn’t sound trivial, it does sound reasonably straightforward.
On a side note, although I wasn’t planning on doing it myself, I thought that a mixture of Biblical text and commentary would be a logical extension to the work I’ve been doing in my Bible wiki. I’ve been trying to build it in a way that makes it easy to extend in various directions. Second in my mind only to dealing with different translations was to consider such commentary.