There's no news of Xu Mengjie joining the cast recently. There was no mention of her plans or projects in the relevant documents. Therefore, according to the information provided, I don't know if Xu Mengjie will join the production team.
Wang Hedi joined the crew in mid-March 2022 to film a series called "Confession at Night." He focused on filming and used his spare time to learn cooking and play basketball. Although there was no more specific information about him joining the crew, it could be inferred that he was actively involved in the crew and focused on the performance of the characters and the production of the series.
Obviously, they will support Luffy all the way. He is their captain, and they have complete faith in him. They have been through so much together, and they know Luffy's strength and determination.
If a marine joins Luffy's crew in a fanfic, it could be quite interesting. At first, there might be a lot of distrust among the crew members. After all, they've been fighting against marines for a long time. But if the marine has a strong sense of justice that aligns with Luffy's own view of right and wrong, they could gradually be accepted. For example, the marine might bring in some new combat techniques or knowledge about the navy's operations that could be useful to the Straw Hats.
A marine who has a special ability or talent that the crew lacks. Maybe a marine who is really good at deciphering ancient texts or has a unique form of martial arts. They would be attracted to Luffy's crew because of their freedom - loving spirit. And once they join, they could use their skills to help the crew in their adventures, whether it's finding a hidden treasure or fighting against a powerful enemy.
In a 'Sabo meets Luffy crew' fanfiction, there could be a lot of emotional reunions. Sabo might share his adventures since they last parted. He could train with the crew members, especially Zoro to exchange sword - fighting skills. And he would surely have a great time reminiscing about their childhood with Luffy.
In this fanfiction, Luffy might be initially in awe of Whitebeard's presence. He could challenge one of the crew members to a friendly spar, like Ace perhaps. And they might share stories about their adventures at sea.
A great plotline might involve the crew getting lost in a mysterious and dangerous part of the Grand Line. They have to rely on each other more than ever and discover hidden secrets about the world and themselves. Maybe they find an island that has been forgotten by time, with technology or magic that is completely different from what they've seen before. And of course, there could be a lot of character - development moments for all the crew members during this adventure.
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.