Now that we know Dragon and the Revolutionaries are planning on declaring war on the world government I think this would be the perfect time for Vegapunk and Kuma to act.
It doesn’t make sense to me that Dragon would send his top generals to attack a highly guarded summit of kings on top of the Red Line surrounded by the city of the worlds most important people, the Celestial Dragons. It would be too dangerous, and you don’t want to lose your top guys this early.
I think it would make more sense for an inside man that has been undercover for years to deal the opening blow of this war. Kuma has been gaining the trust of the Government, even before his mind was “wiped” and now that it has, they don’t even see him as human anymore. To them he is a mindless puppet of war completely under their control and because of that, it’s safe to assume nobody has their guard up around him. If Vegapunk releases Kuma’s mind at the Reverie and takes control of the Pacifistas they can deal a serious opening blow to the Marines, Celestial Dragons, and Mariejois.
Plus thanks to Kuma’s devil fruit, him and Vegapunk could make a quick escape with ease. I think this would also help Fujitora realize his goal as well, because now it’s not only warlords attacking kingdoms but warlords actively betraying the World Government itself.
*Theory by KJB10000