Heading north from Essaouira I'd recommend taking the coast road, to Safi - Oualidia and then El Jadida.

Its a much nicer route than the one on your map except for the industrial area south of Safi and El Jadida. After El Jadida get the motorway, the coast road is slow and tedious.

I am staying in Fez a few months. If you would like local contacts, e.g., tour guide, place to stay, restaurant ideas, etc., feel free to send me a PM.

Does anyone here know where I might rent a motorbike (F700GS or similar) in Fez? I have hired drivers to take me a few places, but I am itching to get out on my own -- on two wheels.

After much investigating, consensus indicated that one cannot rent a bike in Fez. So I rented a car and spent a few days in Chef.

Regarding your Chef-Fez leg, which I followed on my return to Fez:

The majority of that route is in pretty rough shape. As in, you cannot take your eyes off the road for a moment to take in the pretty without risking wonking a tire/wheel in a pothole, rut, washout, whatever. Even being careful I got caught 3 times -- in the car, I was just lucky I didn't blow a tire, but had I been on my bike, any one of those surprises could have made for a bad day. Might have been fun if there were decent sections where one could make some time, rest the brain and body a bit while covering ground, but no such luck. Long/short, not something I'd like to ride, particularly southbound with sun/sunglare in the eyes most of the time. But if others like physical offroad all day, they might find it a good time.