Future of Kidd's story:
Eustass Kidd has a badass design with a badass devilfruit and a badass personality. There's so much that Oda could do with Kidd's character. We still need a Kidd backtory.
Kidd is the rival of Luffy in my mind this is forshadowing for Kidd to be a future villain/anti-hero like magneto. Magneto is an anti-hero sometimes he's good sometimes he's evil. I feel like this will be kidd's role. He will work with the Strawhats against common enemies but won't befriend them.
As soon as kidd master conqeror's haki he has potential to be a future yonko. Though a yonko needs a strong crew and territory, and Kidd is a long ways away from a strong crew. He's gonna need more than just Killer.
If he doesn't become a yonko Kidd could become an enemy of Luffy by trying to kill Shanks. Fighting is fine but If Kidd tries to kill that would be crossing the line. One more alternative is Killer dies and Kidd becomes full on insane like Magneto killing those responsible.
Or Oda just goes the easy route, Kidd gets stronger has 1 more clash with Shanks, from there he just sails the seas as normal and defeats any marines in his path. Then fights the World Government in the final war for his freedom.
Devil Fruit Potential:
Eustass Kidd could do soo much with his devil fruit it's insane.
He could make magnetic barriers for defense.
He could transform into vehicles and giant weaponized robots like a transformer
He could have an attack where he takes a bunch of sharp metal shards and sword then coats them with haki, and gives someone a magnetic attraction charge to stab them.
- Magnetic Flight
- Magnetic Energy Blast
- Magnetic Barrier maybe even give allies a barrier
- Mass control over metal objects
- Mass control over the magnetic field and positive and negative charges
- Creating vehicles, Robots and other objects out of metals
- Lifting people around with the iron in their bodies
- Control of the electromagnetic spectrum potentially being able to appear invisible.
- Control pacifistas
Eustass Kidd could be unstoppable if he reaches his true potential. I doubt Oda will make Kidd that important and strong though.