I had a thought about these two figures using what looks like basically magic. I believe that The National Treasure of Mariejois was an invention made by the Ancient Kingdom that the Twenty Kings took for themselves and now Imu has sole ownership of: A scientific device that functions on tapping into the same energy that makes Devil Fruits possible.
So, Imu uses this device to create all sorts of powers that resemble DF powers, such as the Zoan-like Youkai forms, the Logia-like regeneration and the Paramecia-like teleportation, among other powers. And he can give these powers to anyone he wishes to, such as Pranks and Bandage Betty.
Basically, it's what Caesar and Vegapunk have tried to do, but on a greater scale.