Hello, I'm new to the forum. I've been reading One Piece for the last few months and found it a very enthralling work of art.
Anyway, here's my take on the mysterious "Will of the D". I have three theories. Lemme know what you think:
D: Will of the Dead.
Remember Loguetown? Luffy's words to Sanji and Zoro were, "I'm dead." He smiled really widely, exactly like Gol D. Roger. He wasn't taking it seriously, and neither did Roger when he was executed. Roger even was an ass to the Marines, asking the executioners, "Can you remove this stock? It bothers me."
Which made me think.
What if Luffy, Ace, Sauro, Blackbeard, and Roger are already dead?
I'm not talking anything ludicrous, like zombies or something like that. I'm speaking metaphorically. They're dead, as in the sense that they're people that lived long ago, OR people that lived long ago and exist only in spirit.
During those 100 years of missing history, who knows exactly what happened?
So let's say a group of pirates, or archangels, or fishmen, or people, or whatever… they found a tree that grew akuma no mi. And let's say... It's the Nai Nai Fruit. When they ate it, they died, but were reborn in the form of memories... memories that could be passed down through the ages in various bodies or in the hearts of various people.
Remember how Crocus talked to Roger after the mugiwara left the lighthouse? I believe that he was genuinely talking to Roger, and not speaking post mortem (In the sense someone would speak to a dead relative or friend). These spirits, Or "D's", could be living, breathing entities from long ago that continue to find bodies to inhabit, continue to change history, continue to give people hope.
This, my friends, could be what Clover is going to theorize about in the next manga chapter, and I think Roger found out before he died. Roger discovered that all the D's are living memories, and that his death will mean nothing if he is reincarnated throughout the ages. The Gorosei would be scared of the people knowing this, because it gives a false hope. If they knew that a series of bodiless spirits were going to save them every generation, they wouldn't fear the power of the government. Revolts would start, and people would seek out and gather all the D's together. Can you imagine... All the D's, all the ancient souls of those that ate the nai nai fruit getting together and literally kicking the crap out of the government? Even if they die, it's a simple matter of seeking out the next D and waiting a couple years.
D2: Doppleganger
This one's more focused toward Gol D. Roger, or perhaps even Roger's father.
Barring Whitebeard, Shanks, Blackbeard, and Sengoku (Supposedly), all the strongest people in One Piece have eaten an Akuma no mi. So how about Roger himself?
If you're to believe in this theory, you must first take into account the possibility of a new type of devil fruit. One that is unlike a logia or a paramecium or even a zoan type. Well, maybe vaguely like a zoan type, but the effects don't occur until after the pirate dies.
If what was sat at Enies lobby is true, the "Devil" inside the person takes over the consumer's body and works with them to give them powers. In a zoan's case, it allows a transformation. In a Paramecium's case, it gives the consumer the devil's chemistry. And in a logia case, it directly allows the consumer to completely become whatever element he eats, AND generate it from their body. Luffy can't make extra rubber from his body... if he could, he'd make a fortune as a tire salesman, or something equally odd.
Anyway, so say Roger ate the Doppleganger fruit, or - to give it a japanese name - the tensei tensei fruit. This way, he could laugh death in the face, and still be reborn.
The names are a clue.
Gol: Roger
Jaguar: Saul.
Monkey: Luffy
Puma: Ace
Masuru (If this doesn't mean marsupial, then I'm sorry. My Japanese is limited and I think it does, but the translator won't recognize it): Blackbeard
All animal names, all clues to the fact that they're "One Piece" Of someone really great.
A god, maybe? Poseidon, Pluto? Who knows?
I'll post the third idea after some feedback. I'm still working on it.