I have no clue about the code either. I just know that the beauty of the Taskpaper files is that the files are readable, self-explanatory, and very program agnostic.
Doing something like what you suggested, would break those principles. I don't think that @jessegrosjean will be willing to compromise that, and honestly, I don't think I am down with that idea.
For that reason, all the information on the organization of the tags to accomplish what you mentioned and illustrated need to be done in a separate file, and then be linked to the file where the tags are particularly organized in one way or another.
I think that in order to move TaskPaper into more exciting and possibilities, TaskPaper will have to find a way to sync its preferences and additional file(s) information across computers. In that way, the files produced by TaskPaper remain agnostic, but those that use TaskPaper win a series of new cool "superpowers". Maybe this is something @jessegrosjean needs to start doing in some of his other programs that use any form of markup languages too.
I think that this is a good compromise that not only allows TaskPaper to continue moving into new and exciting places, while keeping its core principle intact. I for one, would love to see something like this implemented, and then extend that idea to files within a library. Then be able to search all the files in the library, and implement a lot of ideas that come with that concept.
Something for @jessegrosjean to think about.