One interesting plot could be Luffy in an alternate universe where he becomes an admiral earlier in his journey. He might use his unique leadership style and devil fruit powers in new ways to uphold the navy's justice while still maintaining his core values of freedom and friendship.
One great 'luffy admiral fanfiction' could be the one where Luffy teams up with an admiral to face a common, extremely powerful enemy. It shows an unlikely alliance and how they overcome their differences in ideology to fight for the greater good.
One interesting plot could be baby Luffy getting lost on an island and Law, being the smart and capable one, finding him. They then form an unexpected friendship and go on little adventures together on the island, like exploring a mysterious cave filled with strange creatures.
One interesting plot could be Luffy seeking out Mihawk for special training to become stronger in order to face tougher enemies. Another might be Mihawk seeing a unique quality in Luffy that makes him question his own views on pirates. And there could also be a plot where they team up accidentally to face a common threat that neither could handle alone.
Nami could also be a common character. She might help Luffy manage the financial aspects of his admiral duties, as well as use her navigation skills to assist in any navy - related voyages. And of course, she'd be there to keep Luffy in check when he gets too carried away.
Another plot might be Fem Luffy traveling to a time in the future of the One Piece world. She could see the consequences of the actions of the current pirates, including her own crew. This could give her new perspectives on her goals and how to achieve them. For example, she might find out that a certain decision she made in the present led to a negative outcome in the future, so she goes back to change it.
One interesting plot could be Luffy's newfound overpowered abilities helping him save Robin from extremely dangerous situations in a more spectacular way than in the original story. For example, he might be able to single - handedly take on an entire fleet of powerful enemies to rescue Robin.
Well, of course, Luffy is always one of the main characters. And then there's usually an admiral, like Akainu or Kizaru. They often start as antagonists to Luffy but then the story might develop their relationship in different ways.
Well, one unique feature is the role - reversal or role - expansion. Luffy, who is known for his carefree pirate ways, is now in a position related to the admirals. It creates a contrast. For example, in some fics, he has to enforce laws which is completely different from his normal 'break - the - rules - to - do - what - is - right' attitude.
In a Luffy x Nami Lemon New World fanfiction, there could be a situation where Nami is kidnapped by a group who wants to use her knowledge of the New World and the lemons (maybe there are special lemons with unique properties there). Luffy, being the fearless captain, sets out on a solo mission to rescue her. Along the way, he meets some old friends and new allies. When he finally reaches Nami, they both realize their feelings for each other have grown even stronger during this ordeal.
The action scenes in 'admiral bobbery fanfiction' can be exciting. Since he's an admiral, there could be epic sea battles. Authors might describe in great detail the strategies he uses, the maneuvers of his ships, and the clashes with enemy forces. It could be really engaging to read about his leadership during these intense moments and how he overcomes difficult situations.