I too have considered the possibility of going to Mori, having been to Maroc twice recently, but 4 weeks IMHO is not really enough. There are loads of pistes in Maroc's south to do, as Chris says. I haven't seen the new Sahara Overland, but do have a copy of the French Gandini book for the south and it's awash with enough to keep you busy for weeks.
Another thing to consider about Mori is that there may be food shortages in certain regions due to the recent locust plague. I don't know just how bad it is, but I for one would not feel comfortable essentially jollying through a starvation zone, so I'm putting Mori on hold for the time being and will go to Maroc again shortly.