The hierarchies in the world of One Piece are a brilliant element of texture that adds depth to the world. Oda took painstaking care to craft a comprehensive system of governance and the bodies that enforce it. The Marines make perfect sense, but the Seven Warlords are another matter entirely.
On the surface, the idea is fascinating and gives the narrative structure - as Luffy has clear objectives to surmount on his road to becoming the Pirate King - but the concept falls apart with a careful inspection. There are innumerable reasons why the Seven Warlord system is incredibly hard to justify logically.
10 Why Are There Only Seven?
One Piece constantly tells fans that there are more pirates than islands in the sea. If that's true, one would think that the Warlords would operate with a "the more, the merrier" attitude. The World Government does choose strong pirates, but even their most accomplished pirate loses to the Yonko. Creating more slots for Warlords increases the odds of the Marines overthrowing the Yonko and tipping the scales in their favor. Consequently, the remaining Warlords could stand as the new top-tier pirates under Marine control.
9 What If They Refuse The World Government?
There's minimal incentive for any pirate to turn down the World Government when they come calling. Being able to pirate freely is literally worth its weight in gold. However, if a pirate were to refuse, how does the Government justify not capturing them at that moment? Furthermore, how would the Government know if the Warlord takes the title but refuses the responsibilities? Fans know that the Warlords do whatever they want. How does the Government punish pirates who resist the call and their responsibilities?
8 Why Is The System Public Knowledge?
The Seven Warlord system would function so much more smoothly if it weren't commonly known information. It's one thing for pirates to be aware of the alliance between their peers and the Orwellian World Government, but it's silly to let civilians know. Also, if the Government concealed their identities, the Warlords might be able to infiltrate other crews more effectively. The World Government is all about concealing their tyranny, and publicly sharing their dealings with the most hated criminal class in One Piece seems counterintuitive.
7 Why Not Equip Them Better?
The idea behind the Seven Warlord system comes from the World Government's desire to catch pirates. Presumably, the Government enlists the Warlords to capture other pirates occasionally. Why doesn't the World Government share resources with the pirates they enlisted as another military branch?
If the World Government offered simple inventions like sea-prism stone or boats that could safely traverse the Calm Belt, the Warlords could be more effective at their job. At the very least, every Warlord should have the six powers under their belt.
6 Why Is There No Marine Supervision?
Following Alabasta, One Piece fans learn that the World Government barely polices the Seven Warlords. They can essentially move unencumbered and refuse to attend meetings. Why doesn't the Government put Marines or CP9 on any given Warlord's ship?
Part of the allure of being a pirate is freedom, so some wouldn't enjoy having a chaperone, but if they wanted true freedom from the Government, they'd never join the Warlords in the first place. The Warlords are a liability; leaving them unchecked is a massive mistake.
5 Why Are There No Term Limits?
The Warlords are seemingly never ousted from their position. Regardless if they perform their jobs decently or not, the Warlords are allowed to remain affiliated with the World Government. Why wouldn't the Government employ a roving membership based on merit? Pirates interested in retaining the benefits of being a Warlord would have to abide by the Government's mandates. Also, if the membership rotated, the Government could pick upstarts as soon as they become noteworthy. Instead, they continue to employ pirates that abuse the privilege entirely.
4 Why Is There No Criterion?
Boa Hancock and Buggy the Clown are both Warlords. The Government employs very little consistency when picking candidates for Warlord status. Why is there no metric of who can become a Warlord? Also, if there is a criterion, why hasn't Oda shared the information with fans? Allowing fans a window into the World Government's selection process could significantly enhance the depth of One Piece. Fans love charting the progression of their favorite pirates with in-universe metrics. Knowing what qualifies a pirate for Warlord would only help immersion.
3 Why Are They Not Informants?
The Warlords are as invested in the pirate world as the characters they're supposed to chase. If the World Government were wise, they would use the faction as an intelligence network. In the One Piece world, there's an underworld that exists outside the realm of regular piracy.
The Warlords attempting to infiltrate the seedier ranks of the criminal underbelly in One Piece would be an excellent use of their talents. In addition, they could keep an eye on shady Marines that are planning to defect.
2 Why Do They Have So Much Autonomy?
Part of the reason the Government invented the Warlords was to elicit a modicum of control on the seas. Ironically, if this is the aim, the Government gives the Warlords a baffling amount of freedom. During his employment with the Government, Sir Crocodile conquered all of Alabasta. At the same time, Doflamingo enslaved Dressrosa. Both incidents caused more of a headache for the Government than necessary. Why give the Warlords such a long leash if they're only going to require clean-up in the long run?
1 Why Allow Them Into The "Holy Land"?
There is no class more protected in the One Piece story than the Celestial Dragons. Most of the World Government exists to protect and support the reign of the unimpeachable sovereigns of the planet. The fact that the Government would allow pirates to enter the home of the Celestial Dragons makes little sense. What if they - like Boa Hancock - have a grudge against the Dragons? What if they're secretly working with the Revolutionaries? There are too many variables to consider when allowing outlaws around royalty.