Rather that having the documentation to an item packaged within the item zip file, is it possible to just provide a URL to the documentation online? It’d make it so much easier to maintain.
I’m using Google Docs to maintain the documentation, and every time I update one of my products, I just download a copy as PDF. It’s much easier for me.
Your idea may or may not be that good, as your site URL may be down or hacked or inaccessible for certain countries. That’s why the included documentation is the best option.