This idea is thrown out in a spirit of playfulness and NOT in sacrilege...
There are people who doubt that the PR step does anything. There are others who have difficulty 1. Defining a purpose. 2. Finding trigger words. 3. Crafting mind-probing questions.
To combat these issues, why not try an experiment with pre-Photoreading?
1. Get a book that you want to experience using the entire PRWMS. Relax and state a purpose like: A. I am PRing this book to enable me to more effectively use the PRWMS with it. B. I am PRing this book to define my most useful/suitable purpose. C. I am PRing this book to determine the most useful trigger words. D. I am PRing this book to craft the most effective mind-probing questions...
2. Photoread the book upside down/backwards. Don't preview it or do anything else to familiarize yourself with the book.
3. Close with an affirmation confirming that you have absorbed the information and are already beginning to [develop an excellent purpose, determine trigger words....]
4. Incubate the book for as long as you feel is appropriate (normal suggestion of 20 minutes to a sleep cycle).
5. Before you begin to process the book in the normal way using the PRWMS, pause to relax. Close your eyes and visualize the cover of the book as best you can. Ask your inner mind to assist you in the prepare/preview steps, using the acquired information. Notice any thoughts, images, or feelings that you get at this point. You may already be getting a sense for a purpose, etc.
6. Process the book as defined by the PRWMS. Notice whether or not the steps that had given you trouble before flowed better this time. Notice if you are more satisfied with the results.
It adds time to the process but you may be surpised at the way in which it confirms that something is going on while Photoreading.