Canidates:
Kuzan: He's with the blackbeard pirates + he rides a bike. (I do believe he knows who it is.)
Saul: He's on Elbaf jerking off or something (Saul is still possible though because Oda can make up some dumb shit)
Dragon: I don't see where he would find the time to do this, but this is the most likely answer. "Flame" tattoo, Pitch Black ship, Weather powers to make whirpools. Most likely has access to a poneglyph.
Scopper: Doubt it. Why would he have a poneglpyh and whirlpools don't fit him, too old
A fishman named Davy Jones: Just my headcanon, Most likely no. (New Character)
A new character: The Lazy answer, possibly.
Final Answer: Monkey D. Dragon or New Character
Kuzan: He's with the blackbeard pirates + he rides a bike. (I do believe he knows who it is.)
Saul: He's on Elbaf jerking off or something (Saul is still possible though because Oda can make up some dumb shit)
Dragon: I don't see where he would find the time to do this, but this is the most likely answer. "Flame" tattoo, Pitch Black ship, Weather powers to make whirpools. Most likely has access to a poneglyph.
Scopper: Doubt it. Why would he have a poneglpyh and whirlpools don't fit him, too old
A fishman named Davy Jones: Just my headcanon, Most likely no. (New Character)
A new character: The Lazy answer, possibly.
Final Answer: Monkey D. Dragon or New Character