The World Government has always viewed Luffy as a nuisance, disruption, threat, etc. He’s the son of Dragon. He wants to be the Pirate King. He disrupts every establish kingdom/area he visits for better or for worse, and makes allies of the most unlikeliest of people. And oh right, he’s officially declared war against them. But one of the most dangerous things about him is his Devil Fruit.
The Gomu Gomu no Mi is essential for the Destruction of the Red Line
The (eventual) destruction of the Red Line will cause physical catastrophe in the world of One Piece, generating Gura Gura no Mi-level activity and Aqua Laguna-sized waves that could drown entire islands and kill countless people. However, an awakened Gomu Gomu no Mi could mitigate and even neutralize this damage by “rubberizing” the environment around it and absorbing that energy.
An awakened Gomu Gomu no Mi user (maybe paired with the Ancient Weapons/another powerful devil fruit user/etc) could be the secret to safely destroying the Red Line and creating the All Blue.
I also think this is one of many reasons why Sengoku claimed Whitebeard could destroy the world, as he was a powerful enough user of the Gura Gura no Mi that he could destroy the Red Line in its entirety. While this wasn’t a dream of Whitebeard, I think he also realized how devastating that could be to innocent people. But I digress!
I think this is the reason why the Marines were tasked with the transport of the Gomu Gomu no Mi and why CP-0 is tasked with eliminating Luffy this arc.
This devil fruit is too powerful in competent hands, and as Law/Kid have shown their awakenings it’s only a matter of time that Luffy awaken as well, which is one step closer to unlocking his full potential as the world-altering Pirate King!