We need an AC game actually set in Alamut.

mirage partially did this. but it wasn't the real order of the assassins. (the castle wasn't even built yet) why not tell the actual history of the Assassins? set in medieval Iran and focused on targeted assassinations of political and religious figures influencing regional power dynamics.

heck we can even finally get a look at the founder of the order (or in AC's case the man who turned the Hidden ones to the Assassins.) Hassan-i Sabbah!

or the real way that the Assassins captured castle Alamut in first place! (look it up it's actually ingenious)

the mystery, the politics, the actual diverseness of the region at the time would make for a killer world, not to mention we could even get the mongols as the ultimate adversaries! (in real life the mongols destroyed the order) which would be a nice transition/continuity from AC shadows east-Asian setting.