My idea on how Luffy will make his super cool entrance is to use the huge cake of Big Mom that she really likes.
You guys probably know the Giant Pop Out Cake or Surprise Cake. Giant pop out cake is made to serve as a surprise in celebratory occasions.
The plan of Bege-Caesar-Straw Hat alliance to assassinate Mama is to first drop the photo of mother Caramel to make her weak for 5 seconds but imagine if Luffy drops the photo of Caramel and also destroy the wedding cake which Big Mom really likes, she’ll probably get weaker two times because two of the things that she really loved destroyed at the same time at the same event which she thought is her happiest day.
*Theory by Fire_Fist_Recca