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While I am applauding your post, I suggest your model does not yet identify what a "wiki" is. Your model also states that a page contains only sections -- that needs some refinement.
I think a "wiki" is a collection of articles and documents, a document itself being a collection of articles. (Incidentally I prefer "story" to "article" so as to distinguish from grammatical and other uses of "article" and it gives a clear path to tie into emerging argumentation models.)
A wiki "story" then is composed of one or more pages. I then look to XSL for the definition of a page, which divides rendition into repeatable header/footer areas & a body area. (In this regard, you can use "heading" or "caption" in the manner that you now seem to use for "header"). A "subpage" is another matter altogether, for its existence is functionally dependent on that of a superordinate page; a subpage often has overflow content from its superpage but it could be an earlier version of the superpage; in other words, a subpage contains material that is effectively attached to another page.
A wiki page is a container for content which, because a single story can be spread across multiple pages, means a single page may contain only part of a story. Page content can be of many varieties, e.g., paragraphs, tables, and lists. Many documents contain titled and sequentially-numbered sets of paragraphs & subsections which we both would call a "section" (as XHTML 2.0 does).
A document is often divided into front-matter, body, and back-matter; I don't believe that a story is similarly divided. Thus the body of a page for a story within a document may be the container for content that is part of one of these three document divisions.
-- John McClure
Inline nowiki and monospace can be totally distinct in Creole (triple-braces for nowiki and double-sharps for monospace).
-- YvesPiguet, 2008-Sep-16