I think Shank’s goal is to maintain balance in the world either indefinitely or until Roger’s successor challenges the world to a fight.
I’ve been pondering this for awhile. If the Roger Pirates reached Raftel, learned the history, found the One Piece, and this is so huge that it will shake the world, why are they (Rayleigh, Shanks, Crocus, Buggy, Mink Duo, Oden) not doing anything and challenging the world? Well, we kind of have the answer to that already.
Whitebeard alluded that someone will find the One Piece, challenge the world to a fight, flipping it upside down, meaning the One Piece will incite a huge conflict. When asked about why Roger turned himself in, Rayleigh told us that he was dying, and it’s implied that Roger intentionally inspired pirates from all over the world so they will seek out the One Piece and inheirit his will.
I think Roger, after whatever he found, wanted to start that world conflict. But he was gonna die soon. He and his crew knew that, although they’d be able to start this huge conflict, without Roger there the entire time, they doubted their capability to follow it through and make sure they finish it. It’s a conflict that will have some purpose and that it must be accomplished. So Roger turned himself in, and the Roger Pirates, are awaiting the day when someone who can finish what Roger wanted to start appears.
Notice how Crocus and Rayleigh are positioned at key points of the Grand Line. It really gives me gatekeeper vibes. Yonkos are the closest, thematically speaking, to Raftel/One Piece. They are the final obstacle for most pirates till they find the One Piece. And I think Shanks specifically is lurking in the New World as a key position. Essentially, they are loosely gatekeeping to make sure the world holds on until when such a worthy successor appears.
All of Shanks actions point toward this. “Meet me when you become a great pirate.” Shanks’ four big moves have been, trying to stop Ace and Blackbeard from fighting, halting Kaido, stopping the war, and of course appearing in Mariejois to warn Gorosei.
We’ve seen nothing but him acting diplomatic. Shanks is going after anything he perceives to be have huge potential ramifications on a worldwide scale to seemingly keep the world stable. I think it somehow ties into waiting for one who can carry on Roger’s will. He’s trying to keep the world in the best state for when Roger’s successor challenges the world to a fight.
Now, obviously, I don’t know if Shanks and Buggy and other lower Roger tier members learned everything about the One Piece with Roger, but if he didn’t I’m sure he may have learned later from Rayleigh possibly, and I believe there’s some loose coordination with him and Rayleigh. I doubt they have some master calculated plan, since after all they do their own things here and there, (Shanks with Makino, Rayleigh with his wife, Crocus looking after Laboon ) but I think that’s the general intent that they follow in the back of their mind. The Roger Pirates, whether some or all (cause who knows about Buggy honestly) are waiting for and keeping tabs on people who can incite and follow through this huge conflict.
The Straw Hat is another matter.
Since the Reverie arc, we obviously have to wonder about its deeper symobolism or functionality(whether it can do stuff or is a crown of Ancient Kindgom like some theorize) but it’s still too early to tell beyond the thematic “it represents inheriting the will”. I think Shanks wearing the hat for a time thematically indicated he was inheiriting Roger’s will, so I think it makes sense that Shanks is trying to support Roger’s last wish essentially, to find someone to start and finish the job he wanted to do. He gave it to Luffy because he bet that it’d be Luffy who’d be Roger’s successor.
This is the impressions I’ve got from Shanks mostly so far. I think top goverment sense that Shanks isn’t gonna start the conflict himself, and that’s why they cooperate with Shanks because he’s delaying that conflict too (although he wants to delay it till true successor appears, the World Government never want to see it happen.)
So yeah, that’s Shanks, he’s essentially gatekeeping the end loosely i think to make sure that the successor is capable of fighting this supposed conflict, and will take it in a direction that Roger wanted. It’s plausible he has more motivations other than this that we haven’t discerned, but I do think this is something that drives the Roger Pirates and Shanks especially.
*Theory by VerusCain