Recently Luffy unlocked a new Gear 5 technique, Gomu Gomu no Gigant, where he expands himself to the size of a literal giant, as if activating Gear 3 on his entire body.
I was thinking about that, and then I remembered that the World Government has done a lot of failed experiments in attempts to “gigantify” its Marines and create an army of Giant super-soldiers.
I think the Gomu Gomu no Mi devil fruit was going to be delivered to Vegapunk so that he could attempt to reverse-engineer it like he did Kaido’s dragon devil fruit or Kizaru’s lasers.
The goal would be to create an army of Rubber Marines who could then be inflated into Giants. Then Shanks stole Gomu Gomu no Mi from Who’s Who, ruining the project (maybe Shanks knew about the World Government’s plans and did it to preserve the balance of power?).
*Theory by Dreadnautilus