Hey guys, I've been on holidays so I didn't post my Imu theory yet. I'm back now and probably posting it tomorrow. Anyways here is a smaller theory, which is not mine but I forgot where I found it. Anyways I can elaborate more on it and also will alter it bit:
The Yonko are based on historical Conquerors!:
Whitebeard: Julius Caesar. His crew is made up of equal divisions (Legions), support by outsider crews (Auxilia). His crew is full of adopted sons. Adoptation was very, very common among Roman Patricians, in fact a lot of Emperors are adopted sons of the former. He gets betrayed by his own adopted son (Blackbeard). Like Casear, Whitebeard was defining of his own era, but never got the title (Pirate King/Roman Emperor). He is also based on Benkei, a japanese Samurai, but all I know so far is that Benkei died standing.
Kaido: Genghis Khan. This one is pretty obvious. The Mongol theme is visually more than evident. The Mongols also tried to invade Japan by the way, albeit they failed. The Beast Pirates are a meritocracy, where strenght determines the rank. His Calamities are based on the horrors the Mongols brought forth, and the cornerstones of their military succes: Fire, Plague and Drought (which causes Famine). Like with Genghis, you don't have to be mongolic to be a Mongol: Queen and Jack are both blonde.
Big Mom: Empress Victoria/Napoleon Bonaparte. Like Victoria, she is female and rules over an empire that includes all races/ethnicities. Tea Parties are a british thing. Alice in Wonderland, which played a huge role in the themes and visual designs of WCI arc, is a british novel. Like Napoleon (which is her hat's name) Big Mom is both very progressive and a tyrant. Both Napoleon and Victoria were monarchs, but it is Napoleon who is selfmade like Big Mom, and he also placed his family to rule over his territories. Lastly there is a very huge number of English and French names in the Charlotte Family, as well as some other European languages.
Which leaves Shanks. The theory linked him to Alexander the Great, citing that he will likely die. But so far that hasn't happened.
However if the Emperors are linked with historical Conquerors, Alexander has to be somewhere and I think I've found him. It's Roger. Everything that the original theory linked with Shanks actually applies to Roger, well the original theory only had that Alexander conquered the world with his friends and died young and that basically made him Shanks, which was kinda stretchy. But it applies to Roger, well at least more than it does to to Shanks. Roger wasn't young but would have died from a disease, just like Alexander actually died from one. While Europeans know Alexander as "The Great", ancient Persians named him "The Accursed". Similarly Roger has also a mixed reputation between Saint and Devil. Both Alexander and Roger had a child with a woman they (supposedly in Alexander's case) loved (Roxanne/Rouge), that child was set up to become the next King by some but ultimately didn't. And most importantly, like Roger, Alexander was the role model for all the Conqueror's that came after him like Pyrrhus of Epirus or Augustus, as well as some kind of proto-Jesus in the sense of a deified human.
Small spoilers for tomorrow as it is a part of my Imu theory: I think Luffy is Jesus and Blackbeard could be Muhammad. While we still have't found out who is Shanks, his ship has a Viking theme, so we probably have to look up Viking History. One thing that immediately comes to mind is not a conqueror but a god, Tyr, who sacrificed his hand, and the interesting part is that he is a variation of the original Indo-European Sky-Father, the main God if you will.
So what do you think? Maybe we can link the other One Piece Conqueror's to historical Conqueror's as well? Someone familiar with chinese history will probably find Chinjao, but Katakuri could be very difficult, I mean probably every historical conqueror was the "perfect man", but I don't think any is famous as a Donut-lover.