Yes but why Big Mom's bloodline ?
We know from Kaido that Vegapunk was experimenting with Yonkou Lineage Factors. Cipher Pol is seen in both Whole Cake Island and Wano; it would not be hard for elite agents to find DNA of Kaido and Big Mom if they needed it, and they already had Kaido's lineage factor from his time imprisoned.
So, Bonney would be a failed experiment of a Big Mom clone, tying her into Sanji's failed-soldier-of-science plotline.
Also, just look at Bonney. She acts exactly how a younger Big Mom acts, doing whatever she wants, eating a shit ton of food, and acting moody and vengeful. If you compare their characters, Bonney has Big Mom's personality, but Ginny's body and tactical skills.
Both characters are associated with, what? Spying, with Ginny being a wiretapping expert, while Big Mom had the greatest intelligence system in the pirate world.
I still think we'll see Seraphim Yonkou, though. Garling raises Seraphim Shanks?