TES VI can't be in Alinor, because if the player chooses any race but Altmer or Bosmer, they will be killed on sight. Kind of hard to play a game where every sentient creature in the gameworld wants you dead. It would be even worse if you could play as a human and the game just pretended that no one in Alinor realizes that they're supposed to be lynching you. I would love to play in Alinor as an expanded adventure game, however, it will never work as a full game because people would [censored] about not being able to play as a nord or whatever.
Bethesda is not averse to creating their own reason for a game to be set wherever the blazes they want it.
Maybe we begin as a slave, and there's an uprising. There are dissidents among the Altmer, who knows what agencies they would employ... Alinor may bend to the Empire of Man. Or perhaps Thras encroaches, and Alinor summons the "All Flags." Maybe the Maomer take Alinor and pose a wider threat to the Empire of Man. Anything is possible. We were argonians in the most xenophobic province, why not again?
Another point is to make is that non-argonians can't really survive in Argonia. Which kind of rules out that province as well.
It's only the deepest region of Argonia which is inhospitable, and that would make the small province a bit more like Vvardenfell, with the huge mountain we needed to walk around.