I think one of the issues with depicting anything in central Australia is that, while it is possible for people to live there, it's not possible to do anything on the sort of scale measured by a grand strategy game. Yes, there's lots of tribes in those areas, but you wouldn't exactly build a city out there, or someone would have done so already.
That said, I do think it would be good to give a nod to alt history by allowing a sufficiently determined player (or maybe a native faction with some inbuilt bonus) to have at least a light presence further inland, especially to access Australia's enormous ore deposits. I could imagine a tense and exciting moment around someone marching an army briefly through the Simpson desert, knowing it will suffer brutal attrition, but that their unprepared enemy will have no defences against a flanking attack more audacious than anything they imagined. Alternatively, native tribes could use this space as a staging ground for guerilla warfare against colonial powers that would fall prey to the desert itself if they were careless in their counterattack. It'd be like Dune, but with a lot more beer and foul language (so, more like the books).
As for how to depict native tribes themselves, I think there are a lot of fascinating differences between them and what we think of as conventional Western civilization. People talk about the different beliefs of tribes, but even the core cosmology of Aboriginal tribes is mind-bending compared to other religious frameworks. They typically hold that all their mythology takes place outside of the time-space continuum, in a sort of parallel plane of existence where everything happens simultaneously at all points in time (or at least that's my understanding of it). Depicting any part of Aboriginal society in a game built to simulate European powers is going to be an enormous challenge with a lot of details lost in translation, and I could understand any company being hesitant to take on such a task.