I think there’s something about the medium of a document, a thing with a reader/viewer and an authoring tool, that you can send to people and they can send you ( fully specified rather than just a URL) that is distinct from what the web is.
It may seem so obvious that it is almost invisible, but there’s something very powerful about organizing a form of content of a medium into a document format. Shareable, distributable.
It may be an imprecise analogy or example from a non-expert but humans had writing for a long time before we really created documents like account books, printed books, legal contracts, all these genres of documents, somehow lifts whatever it is that writing is, into a new form and power by virtue of them being encapsulated in a document. In a similar way that the creation of video movie and song documents (cassette tapes records, VHS, film emulsion, etc.) lifted visual and audio information into a new, medium and power, because these documents became first class currencies of exchange of that.
I just think the same as possible to lift web writing, so Web technologies into a document format as well.
A small, but non-trivial part of this is that zipping a website and sending it it’s not really a hackable document in the same was DOCX is, and it won’t display in the same way as a regular website if you serve it from files.
Is it the WYSIWYG you want? Why not just send an actual document then, like Word or LibreOffice?
Maybe I'm misunderstanding what you mean by "hackable", but I'd have thought PDFs were the least hackable. They're notoriously hard to edit.
While it’s true PDFs are hard to edit, I mean anyone can author a PDF…and probably in some circles far more people know how to create a PDF and they do create a website.
It’s not really the W7 it’s more the richness and ubiquity of web content, has so far eluded encapsulation in a document format.
I’m sorry the idea so out there! Haha :)