Wow, I never got around to reading the books, and sadly all I can contribute is from the movie. That being said, I find the concept worthy of making a good campaign.
You can keep the desert flavor and have purple worms, or something based on them as the worms being riden. You could also change the desert to artic and have the white worms or in
FR I recall something about a monastary riding Rhemoraz(sp).
I also like the element suits they wore that protected them and recycled the water. These could be a type of mundane armor or a magic item. Maybe a enchantment you add to any armor so everyone could get it.
Some of their sonic pulse atks could become powers. Not sure if these should be added to a class like the invoker or the wizard, or be a paragon path where more classes could take. It may depend on the length you plan to run the campaign.
Maybe 'spice' becomes 'residium'. This would have the wizard ruled empire trying to gain control of all the production and distribution. Side fractions try to atk caravans and set up their own mining operations. Add in the locals that worship the worms and the reduction in residium is causing low birth rates in the worm population, you start to have lots of conflict.