French Claire,
My immediate response to your posting on this topic was resistance. Like Successful, I believe that everybody is unique - and that seems to suggest that the road from 'where I am' to 'where I want to be' will be specific to each unique soul (to borrow from another colleague's ID) However...
I've been thinking about the number of the personal development books and 'courses' I have purchased and worked with in recent years. I have noticed that while each has his own approach to the topic, the underlying plans are very similar. Still, I expect each one works better for people who might belong to different niches. I have found in teaching/learning situations, that being able to approach information from a variety of perspectives makes me a much more effective teacher/learner, so I am grateful to have been exposed to these different 'road maps', so to speak.
Still, it is possible to be flexible in which way you approach a problem only if you have a big picture - a really long-distance view - or you might say 'eternal perspective' on the question. To use your mapping analogy, I really dislike using 'Map Quest' because I get such a limited view of how to get from here to there. I much prefer using a paper map which gives me a big picture of the main roads and how they interact with each other. Then, if necessary, I can use a close-up view of smaller streets with their peculiarities (like one-way or intermittent streets) to complete my journey. Likewise, if you really understand the theory, you can see how different approaches can work to get the desired results. If you don't really 'get' the theory, but only know one road to your goal, you become inflexible, stuck, and frustrated.
So... I believe there is an over-arching road-map to personal joy and peace and progress. Frankly, I believe that the basic precepts offered by most religions (but not the individual routes promoted by some) give this global 'road-map.' The general directions for getting there are the same for everybody. However, the specifics of the trip will be unique to each individual that travels. - Back to the road analogy - each will encounter different traffic patterns, detours, road conditions, etc. Some may choose to drive, some ride with others; some bicycle, others walk at various paces. Some will follow the roads or paths that are proven and well-traveled, others will wander in their own ways. From this perspective, the project of producing an A-Z instruction manual that would be 100% effective for everybody becomes an exercise in futility.
But this is not intended to discourage you from your grand goal, but perhaps to help you define it. If you are able to put the big picture into words, pictures, metaphors, etc. that communicate it better (or perhaps just differently) than what is already out there, you do indeed have a worthy project that could be a great contribution to the world.
May you create peace and joy in your day.
Margaret Ida