You might consider cactus fruit to endure the drought periods as I read you face similar HOT DRY periods as we do here in FL (helps motivate my fondness of them). In particular fruiting jungle cacti (that just love the water whens it comes). Also succulents such as Chaya Spinach Tree would be a dream there. These are just off the top of my head of course, but with these particular examples they're extremely easy to propagate, nearly year round, meaning they have the potential to be 'spread' much faster than just about anything, with rather short waits specimen to specimen to get actual yields.
From there, the bigger picture I see for their troubles includes trees with dense roots, or possibly more importantly trees with deep taproots. The fast growing kind. Not for food, but to stabilize the earth there. I'm not sure about their root systems, but some of the biggest trees in the world are in the Eucalyptus family and they can easily grow 10' a year, to reforest that landscape.
I don't normally go making lists of the latter there, but seems it'd be important work.
Don't think to far into ornamentals too often but do absorb them, none the less, while many the edible perennials I chase end up having ornamental value. Perhaps the coolest feature of my yard is my 7' tall giant Asiatic Spider Lily. The flowers are giant, but odd. Pretty neat but the plant itself is the lushest jungle foliage one might hope for. Real popular here as a landscaping feature, especially out in the mini earth islands in parking lots (without irrigation). Those dont often look too choice but the giant cluster in my yard under the shade tree is bigger than all the sites say it should be. The other awesome feature I've 'built' is my 'forest' of huge Sword Pear cactus. It's a real force of nature this lot, and it makes impressive night blooming flowers, real big but not giants like the dragon fruit genus. Shampoo Ginger is a nice looking ginger, the stands I collect from are about 8' in height by years end. They die back here in the winter, but the fall flowers that provide choice natural shampoo are worth consideration. I've been growing cassabanana vine here a few years this thing is always blooming when its warm out, very impressive but haven't figured out how to fruit it yet while I haven't started cloning it yet and dont have prime supply on seeds worth noting either. Outside of that lot, well, wrong forums.