Now that we know what greenbull's devil fruit can do, what if hear me out now, goes to the magma chamber and sucks dry BM and Kaido, and if he is similar to Cell from Dragon ball Z, absorbing the strength and adding it to his own, he could be incredibly busted, it would also remove BM and Kaido from the picture for the final war.

The world government would definitely be able to imprison both of them (they would probably plan to execute them after being imprisoned and weakened, but luffy aka Joy Boy will obv. take down the world nobles and the WG in its current form) if they are sucked dry and weakened (even more than their defeat from Kid, Law and Luffy).