The Assassin's Creed series is definitely a deep dive through time. Though the gameplay is inconsistent, these titles always provide sprawling, detailed recreations of pivotal moments in history. However, many more periods remain unexplored.
The 19th century, for instance, is rife with opportunity. It was a period of rapid expansion the world over. This would be a prime chance to mix up both brands of Assassin's Creed gameplay. Moreover, it would let storytellers delve into how these tremendous changes impacted societies on a human level.
6 The Napoleonic Wars
Considering Ubisoft's French roots, it's surprising that the developers haven't tackled an iconic figure like Napoleon Bonaparte. That's not to say he limited his imperial pursuits to his native country; his military conquests expanded across Europe. Numerous countries and cities became contested battlegrounds. This would obviously lead to several sandbox environments for players to explore, keeping in line with the AC's recent RPG approach.
The setting would also hearken back to the series' social stealth roots. The period saw political maneuvering on all sides to maintain resources for the war. People often resorted to backstabbing and manipulation to get the desired outcome, as seen in works like the Sharpe stories. That merging of espionage and open warfare is right up Assassin's Creed's alley.
5 The Meiji Restoration
By the 1800s, Japan had largely become an isolationist country. This did not sit well with foreign peers. It was the United States who took the next step, placing gunships outside the Edo capital. This forced the Japanese to reopen trade routes, which, in turn, led to many governmental reforms and innovations.
Assassin's Creed thrives on portraying such pivotal events. The parties in these games often take radical action to set the world on the "proper" path, and this would fuel their involvement in the gunship blockade. Some characters may want to open trade to stimulate the global economy while others might spit on foreign intervention undermining a country's freedom. One could easily make a case for either side.
4 The Rise Of Shaka Zulu
One of the most prominent tribal figures in history was Shaka Zulu. Coming into power in Africa, he swiftly asserted himself through political stratagems and societal upheaval. However, these paled in comparison to his military reforms. Using new weapons and tactics, he revolutionized his armies and made the Zulu nation a force to be reckoned with. Someone of such global strength would get the attention of foreign powers, such as the Assassins and Templars. Unfortunately, that attention may be a target.
Shaka's pursuit of war was controversial. His attacks cost a huge portion of the African population. Both sides may want to stop him for that reason, as the ends may not justify the means. This could naturally tie into his actual assassination by his half-brothers.
3 The Founding Of Deadwood
Another setting Assassin's Creed hasn't explored is the Old West, and Deadwood would fit like a glove. Established by gold miners, this town was as dangerous as it came. Crime was rampant, with regular thefts and killings in the street. This would obviously make it a challenging hub to navigate, but not as challenging as its social significance.
Deadwood was uncharted territory. It was built within South Dakota yet was largely lawless. Much of its conflict stemmed from how it could legally operate and if/when it would fold into the United States. The Assassins and Templars would naturally want to influence this in some way. In particular, the former would potentially oppose a governmental takeover due to preserving natural freedom. Everything is permitted, after all.
2 The Taiping Rebellion
The Assassin's Creed games usually deal with ancient artifacts and holy powers. In the face of such power, a person would naturally develop delusions of grandeur. Such was the case with Chinese leader Hong Xiuquan. Believing he was Jesus Christ's younger brother, he established his own religion and led a bloody crusade across his country.
Such insanity is nothing new in Assassin's Creed. A similar affliction befell Cesare Borgia in Brotherhood and Sigurd in Valhalla. Both cases stemmed from grand promises made regarding an Apple of Eden or some other mythical object. The series could easily frame Hong's turn the same way.
1 The Musket Wars
This was a period of tremendous loss for the New Zealand people, one of their own making. When a group of Maori tribesmen gained a supply of muskets, they promptly turned on their brothers. The result was intertribal war; killing and enslavement were committed on all sides. The whole episode stands as a chilling lesson on power and its responsible use.
This theme permeates Assassin's Creed. Many characters fail that test when handling holy artifacts and Isu devices. Seeing that scenario applied to more worldly objects would make a novel change. It'd present the same message, yet the tale would be more relatable. As such, the Assassins may still step in to restore the balance.