It'd be quite poetic if Oda writes final villain to be a woman just like how the first villain was a woman, but man, Alavida was ugly and fat before becoming beautiful from her eating a DF
Also, we need to remember that Robin was sort of a neutral villain, but Hancock was a villain for Luffy before falling in love with him, also Luffy clashed with Big Mom but yeah, BM was ugly and fat, also Uta was an Anti-Villain for the One Piece Film Red.
Edit: I hope Imu is a female villain, can become both pretty and scary, pretty as her normal form, scary like if she's Dormammu, Amatsu Mikaboshi, Alucard, Father from FMA, Ryuk...etc, just like how Kaguya whom is the final villain of Naruto is a Female, and I hope Uta becomes Canon and her powers too, I'm also getting kinda tired of how Oda making Females pawns and weaklings, like how he did with Sugar or Baccarat, I hope he makes Shirahoshi strong and confident and has control of her weapons.