It would be a wild combination. Vegeta's serious and prideful nature would contrast with Luffy's carefree attitude. But his combat skills would be a great asset. He could probably take on the toughest enemies easily. He might not get along well with Usopp at first because of Usopp's cowardly tendencies, but over time, he could teach Usopp to be braver. And his presence would make the Straw Hat crew even more feared among their enemies.
The order in which the main characters of One Piece joined the Grass Hat Pirates was as follows:
1 Monkey D Luffy
2 Nico Robin
3 Franky
4 Choba (Chopper)
5 Brook
6 Sauron (Sengoku)
7 Nami
8 Usopp
9 Sanji
10 Nico Robin's father
The above are the original members of the Hat Pirates. As the plot developed, Luffy, Nami, Usopp, Sanji, Sauron, Choba, and Franky joined one after another. Nicole Robin also joined the Hat Pirates at some point later.
The Straw Hat shinobi could be a new character who combines the characteristics of both Naruto - style shinobi and One Piece pirates. He might wear a straw hat like Luffy and have ninja abilities.
Well, it could be about a shinobi who somehow gets involved with the Straw Hat crew in a world where Naruto and One Piece universes collide. Maybe the shinobi has some special abilities that are useful to the crew on their adventures.
The crew would be really curious. They might see Luffy's father as a powerful ally. It could also boost their morale, knowing that Luffy has such a strong family connection.
The Straw Hat crew would have a mix of reactions. Franky might start building a special nursery on the ship, using all his engineering skills to make it safe and comfortable. Robin would be a source of calm and knowledge, sharing stories about pregnancies in different cultures she's read about. Brook would be playing gentle music to soothe Nami. And Luffy, as the father, would be constantly by Nami's side, sharing his positive energy and telling the baby stories about their adventures, even though the baby can't hear them yet. Overall, the crew would come together to support Nami and the new life coming into their world.
Nami would probably be devastated. She has been with Luffy through so much, and his death would be a huge blow. She might become more withdrawn and serious, as Luffy was often the one to bring out her lighter side.
Another scenario could be that Hancock's presence causes some internal conflict within the Straw Hat crew. Nami might be a bit wary of her because of her past actions and power. Chopper could be curious about her Devil Fruit abilities. Zoro might not trust her easily. However, in the face of a common enemy, they would have to put aside their differences and work together. Hancock might learn a lot from the Straw Hat crew's camaraderie and freedom - loving spirit, which could change her perspective on pirates in general.
For the Straw Hat crew, it would be a major shift. Sanji would be beside himself with excitement, always eager to please and protect. Zoro would have a complex reaction. He might be a bit more gentle in his challenges to her but also be on high alert to make sure no one takes advantage of her. Nami would be thrilled to have a female companion on board. She could teach Luffy about things like haggling in a more feminine way. Usopp would be the one to spread the news around the ship in his own humorous way. Chopper would study if there are any health differences for a female Luffy. Franky would be focused on making the ship more comfortable for her, like adding softer seating areas. Brook would be using his skeletal charm to make her laugh and keep the crew's spirits high.
Well, Naruto's skills like his shadow clones could be a great asset. He could use them for various tasks on the ship, from cleaning to helping in battles. His determination would also match the Straw Hats' spirit.