Would a dedicated desert pack representing this biome not be a better fit?
Not unless it's only got Middle Eastern animals in it, which isn't likely to happen.
It's not so much about regions that have to do with zoos' curriculums, it's about filling out the roster. A good example is that North America and Europe mean
absolutely nothing to me in terms of real-world zoo-focus, because neither of these regions is well-represented in most Australasian zoos. Conversely, New Zealand might have no focus at all to any zoo you're familiar with, but in terms of conservation and education it's literally
required for a zoo to function in New Zealand that it has a strong focus on the protection and breeding of our native species.
It's also about filling the roster with
common zoo animals. For the Middle East, several species immediately come to mind; the Hamadryas baboon, since it was skipped out of Africa; the dromedary camel, which we have
myriad pieces of scenery for; the rock hyrax, perhaps a little less considered, but very common in captivity; the caracal, one of the most commonly-held small cats the world over besides the serval; and of course there are species there that are crucial to global conservation efforts, such as the Arabian oryx or Persian onager, and, if we ever get them, birds like the northern bald ibis.
A Desert Animal Pack could include some of these species, but it would also likely include animals from central and northern Asia, North America, and Australia.
Honestly, if we get biome packs instead of region packs I won't complain, as I don't think it's a
bad idea, but that doesn't mean there aren't considerable options for more region-based packs going forward.
(I'm also going to take this opportunity to plug Japan as a good choice of region pack, too; the red-crowned crane, Japanese serow, raccoon dog, and sika deer would make great habitat animals, and I'd love the fire-bellied newt as an exhibit animal, and although the East Asia theme does cross into Japanese bits quite significantly the Africa Pack shows that they can expand on an existing theme or building set with new items).