I finished reading through the books last night trying to figure this out on my own. I concluded that I could get Maxim in him in about 10 weeks and Chreia in 20 by reducing the number of writing assignments, number of sentences shuffled, etc. My reconfiguration doesn't exactly match yours, but I'm relieved to know that this worked well.
I had considered completely skipping certain parts, as an example, memorizing the parts of the five paragraph essay and instead focusing on the types of paragraphs. He already knows the parts of the essay, and many other things, so I had planned verbal confirmation followed by a lesson only if needed. I think this could reasonably reduce the time needed in Maxim to only 7 or 8 weeks, though he may have learned more from Skills for Rhetoric than I thought.
I do not currently own a copy of Herodotus. I understand that all the material in Diogenes is important and foundational, but is there something key that students often have trouble with that prevents success with Herodotus?