There isn't really any way that the narrative can allow a game set in Feudal Japan. Not only that, however, but its a tired and used setting (mainly in Japanese media, of course) that wouldn't lend itself well to the AC series, which is brilliant at urban areas and fairly poor at anything else.
Conversely, the 3rd Crusade and Renaissance Italy were almost totally unique: I'm not just talking games either: in media generally, these periods are very rarely touched upon, and also have a rich history of assassinations and murder plots.
Another setting would need these two things: Uniqueness and wealth of historical assassinations
Egypt during the height (or maybe decline) of the Pharaohs could be very interesting, the details of which being vague enough to let many things happen.
Russian Revolution could also be an interesting one: the Word of God in the series already says that the fight between the Templars and Assassins was raging in this conflict, and there are many historical figures such as Rasputin to take advantage of. In canon it is probably the largest victory the Assassins have won in centuries: they caused the fall of the Tsars, who were templars.
Victorian England. Not original, but interesting: a Sherlock Holmes-esque portrayal with a gritty take on things, joining the two separate worlds of the corrupt and scheming rich and elite and the grimy, dirty creation of the criminal underworld.
A lot could be done with such a setting.
In summary: Feudal Japan is a terrible idea.
Conversely, the 3rd Crusade and Renaissance Italy were almost totally unique: I'm not just talking games either: in media generally, these periods are very rarely touched upon, and also have a rich history of assassinations and murder plots.
Another setting would need these two things: Uniqueness and wealth of historical assassinations
Egypt during the height (or maybe decline) of the Pharaohs could be very interesting, the details of which being vague enough to let many things happen.
Russian Revolution could also be an interesting one: the Word of God in the series already says that the fight between the Templars and Assassins was raging in this conflict, and there are many historical figures such as Rasputin to take advantage of. In canon it is probably the largest victory the Assassins have won in centuries: they caused the fall of the Tsars, who were templars.
Victorian England. Not original, but interesting: a Sherlock Holmes-esque portrayal with a gritty take on things, joining the two separate worlds of the corrupt and scheming rich and elite and the grimy, dirty creation of the criminal underworld.
A lot could be done with such a setting.
In summary: Feudal Japan is a terrible idea.