Once Luffy is kidnapped, Doflamingo might try to break Luffy's spirit. But Luffy being Luffy, he would resist. Meanwhile, the crew's journey to rescue him could be filled with many obstacles. They might encounter other pirates or marines who are either allies or enemies of Doflamingo. The crew would have to fight their way through and use their combined skills to reach Luffy. For example, Brook could use his soul powers to pass through walls and scout ahead.
Luffy's victory over Doflamingo in the manga was a combination of factors. His growth in strength, his unwavering will, and his ability to adapt to Doflamingo's tactics all played a role. Additionally, the support of his friends was crucial in tipping the scales in his favor.
Well, in this scenario, Luffy's crew would surely go all out to rescue him. Nami might come up with a clever plan using her navigation skills and knowledge of the area where Doflamingo is likely to be hiding Luffy. Zoro would be ready for a fight, his swords sharp and his determination unwavering. They might also get some unexpected help from other characters in the One Piece world who have a grudge against Doflamingo.
One popular plot is Nami getting into trouble during a treasure hunt and Luffy coming to her rescue in a really heroic way. This showcases their strong bond and Luffy's loyalty.
Some Tumblr blogs are also dedicated to One Piece fanfiction. You can search for tags related to Nami and Luffy on Tumblr to find relevant fanfictions.
Luffy is still alive and kicking in the manga. The story keeps evolving with him at the center of the action, encountering new enemies and growing stronger.