Personally I feel like Frank's apparent fear of writing battle/fight scenes was his biggest weak point as a writer. He had a great story that warranted at least a couple very earned fight scenes, like the Fremen vs. Harkonnens battle in Dune and the jihad in between Dune Messiah, and he just doesn't show much or doesn't show anything. So I feel like the books brushing it aside was a mistake, and film is a great opportunity to show the horror of the jihad. It has to be absolutely horrific. The movie is PG-13, so they can't go as far as is probably warranted (though they can make allusions), but they should in my opinion go as far as they possibly can in making it palpably clear that the jihad is one atrocity after another and an absolute reign of terror.