For nationals and expats the routes are completely different. Nationals are the only ones who get local labour contracts. Expats are hired exclusively via crewing agencies, mostly Sigma and CAE. Also, the zero-experience options are open to nationals only. So, if you are willing to commit to Air Astana long-term, getting a passport (maybe as a second citizenship?) might be worth looking into.
As for the prospects - plans are changing as fast as the situation... There have been talks of postponing the big Airbus order, establishing a cargo division with the B767 and whatnot else. Hopefully the dust will settle soon enough so that there's a more clear picture of what Air Astana and FlyArystan will look like post-COVID. But I am reasonably optimistic about the outlook, bearing in mind the geography of Kazakhstan and the fact that on most origin-destination pairs flying remains the only practical way to get there and back within a reasonable time period.