Your post is very interesting. I would contend with one little word choice: “arid wastelands.” Deseret was indeed arid, but hardly a “wasteland.” According to my botany professor in college, when the pioneers first settled Salt Lake Valley, the native grasses grew so high that people regularly lost livestock.

I doubt different political boundaries would have changed much. Utah Territory wasn’t all Mormon, and Mormon towns were established in the surrounding territories all the same without benefit of the State of Deseret. The early abandoned places like Las Vegas and the Muddy River would have been no more sustainable at that time had they been under the jurisdiction of Deseret. The reach of the Saints in the Great Basin was constrained by their numbers.