I'm not a Sanji fan, first and foremost.
"Hanagata" has factually been used as plural before and was the main choice for this line by both official and non-official translators.
The scene is about two raising stars (which "hanagata" commonly refers to) taking over the Old Era (Marco) to take the current lead performers (King and Queen) down. That's the narrative here, which is why the whole storytelling parallels Zoro and Sanji as opposed to King and Queen, whose condition of performers (the two of them) is what lays the foundation for Marco using "hanagata"; therefore needing two new stars for the two old stars. Unlike previous skirmishes, this scene marks the actual start of the final, one-on-one clash that will take King and Queen down; hence why it's now stressed the meanings of the New Era taking over and Luffy getting closer to his dream of Pirate King thanks to his Wings.
You are free to keep thinking it's about Zoro physically coming to the stage. Makes zero narrative sense and it's significantly more clumsy and naive, but go ahead; how you say Zoro is the only option that makes sense in spite of the huge metaphorical weight in my version compared to your simplistic approach is enough for me to give up on you.
Marco gives up on the two lead performers; then speaks of "hanagata" taking over (Marco representing the Old Era); then Zoro and Sanji strike King and Queen together; then they reflect on how this will help Luffy achieve his dream (bringing the New Era); then the editor adds a note referring to the appearance of the two Wings...
...yet it's all about Zoro physically coming to fight. Can't help it.
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I'm not a "sanjistan", said tons of times my favourite Straw Hats are Jinbe, Usopp and Franky and I've publicly criticized Oda's handling of Sanji as a character.
Marco is talking about actors taking over him in order to face the lead performers. "Hanagata" is used because of King and Queen; "star" isn't a translation void of context, it needs King and Queen to make sense, and therefore Zoro and Sanji as those dethroning them from then on and taking their spots as lead actors.
The context requires two actors (young starts, more precisely) because it begins with another two well-established lead performers.
And surely I'm the sad one, not the man-children here understanding Marco's scene the way Ron Swanson understood
Moby Dick:
"Marco meant the two actors of the New Era taking over himself, a remnant of the Old Era, in order to defeat the lead performers King and Queen —hence using a kabuki term commonly meant for young stars, with the next scene wholly depicting Zoro and Sanji together as they definitely confront Kaidou's top men to help Luffy bring the New Era? Haha, no, it's just Zoro stepping on some floor".