Been thinking and came up with the following



Tanger Med
Chefchoen
Fes
Rabat
Azrou
Middle Atlas Pistes
Midelt
MH2 via Imichil & Todra Gorge (all tarmac now)
Tinerhir
Desert Sculpture
Erfoud
MS6 to Zagora

Then the 2 red section would be good options

To the East
MS4
MH10 through Jebel Sahro to the Dades Gorge and Ouarazazate

To the West
MS5 to Foum Zguid
MA9 to Tazenakht over the Issil Plain
MS9 to Ouarazazate

Back to the white routes
MH7 Ouarazazate to Taroudannt (go to Ait Benhaddou on the way out of Ouarzazate
Taroudannt to Marrakech on the Tizi n Test (stop at Tin Mal on the way)
Marrakech to Essaouira
Essouira to Tafroute via Cascades D'Immouzzer (see the blue rocks at Tafroute

From Tafroute Morocco Overland has many options heading south or take the road to Sidi Ifni before heading south to the Western Sahara.

Only 2 wallled cities and imho the best. I don't really like the North of Morocco so can't comment much. Volubilis Roman ruins is ok and Fes very much on the tourist trail. (When I visited I didn't like it and haven't been back)

This cuts out your long trip back up north from Marrakech to Rabat for Visa's and probably a boring drive.

Matt (twenty4seven) probably has more experience of the pistes than I do. I think my suggestion gets in the classic sites of Morocco with some good suggested piste section based on my trips and takes in all main mountain ranges and different scenery until dropping south from Tafroute.

Give me a shout if you'd like track logs, kmz files for GE

HTH

Mark