I agree with everyone else here. Fletcher's book in its various editions is the gold standard for hiking books, primarily because of his approach, not the specific gear recommendations. For better or worse, the Internet has largely replaced books such as you are contemplating, while making it much easier to write one. Oh the irony of it all. Just as with other markets, audiences, and activities, backpacking has gone from a fairly standard set of "what everyone should own" to many different styles and types of hikers, who can communicate and form communities over long distances. Just looking at stoves for example, there are so many different types for different purposes that saying that one particular stove is the "best" is meaningless. Another example is the choice between synthetic and down bags or insulated clothing. In my profession, my first reaction to a question with multiple possible answers is usually "it depends" and I go from there. Laying out a book that way could be a great help to beginners- I can see a book with lots of charts and decision trees with pros and cons of various items by class, not so much brand as being useful.

Your idea is admirable, but unless you plan to be constantly revising the book, which you could do with an ebook, traditional publishing would be a tough sell.