He will certainly claim it, by doing something mindblowing and causing havoc somewhere
Like when he beats an Admiral and does something afterwards (or at the same time)
During Mr.Prince moments, Sanji is always by himself doing his stuff through the shadows, although Luffy and Zoro can be aware of that if Sanji wants to (like during the Sea Train)
The "most feared man by the marines" could go on as a legend of the guy who did something insane in the name of the Strawhats (meaning he was alone, obviously, he needs to be the center of attention), mind you that Sanji already took the Captain role before
So don't worry, there are many possibilities, thats a given...