A good way to describe your feelings about it.
spoilers:end of spoilers
I'm going with 'power' because of the World Government's previous actions. They generally try to gain or destroy anything that they feel is a threat to their control, whether it be a person, weapon, devil fruit, or knowledge. They had the Shichibukai in an attempt to further control the seas, and disbanded them when it was revealed they weren't living up to their end of the pargain. It's why they've tried their best to hide all knowledge of the Ancient Weapons. It's why they used a Buster Call to destroy Ohara and killed everyone who lived there (save for Nico Robin). It's why they're so terrified of the Yonko, because each of the Yonko equals them in power, so can't be controlled.
And for them to be so gung-ho about keeping the Gomu Gomu that they'd use a rival to Rob Lucci as a guard, then throw him into Impel Down when he fails, the Gomu Gomu has to threaten their control in some way. And as it's a fruit, that means it has to be the power that it can bestow upon those who eat it.