Leather in Morocco
I rode round Morocco 2 years ago in Black leather jacket with cotton lining and Draggin jeans. Our route went over desert pistes and some tracks in the High Atlas. Never had a problem with heat.
My buddy had nylon jacket and MX pants and sweated like a pig, he was constantly adjusting the zip of his jacket to manage the heat.
I had some old belstaff leather jeans which had cotton linings in my luggage. I didn't wear them in Morrocco was because I liked the filthy patina my Draggin jeans were developing. ha ha. You can often see the same Belstaff jeans on ebay, for less than £50 second hand.
In summary, cotton lined leather jeans are available, and they're great for Morrocco.