Luffy going along with this plan sounds extremely out of character. I was expecting luffy to say "Nope, I'm fighting Big Mama face to face"
Assassination seems really weird for the Luffy crew.
Luffy isn't Goku. He may have a sense of honor, but he fights for his friends/to win, not for the thrill of the battle. He and his crew just aren't much for elaborate plans, either, or the plans they're in tend to fall apart, so you get a straight fight instead of some trickery.
Luffy knows his goal and knows when a foe is out of his league, like in the Paramount War where he threw seawater-soaked masts at the Admirals to distract them while he dashed in for Ace. Goku would've gone in for the fight.