Vegapunk has a secret ally on egghead that he could call on, however if he does so, that person will be put at risk. Who could this person be? imo, the most likely answer is sabo.
Sabo was heavily featured in chapter 1060, which happened right before the start of the egghead island arc. Sabo was hit by Imu's weapon and was presumed to be dead.
Then during egghead island, we learned that Vegapunk has ties to the revolutionaries.
Now, Lucci is trying to destroy the Sunny and Zoro is occupied fighting zoro. Who could possibly show up and help Zoro to save the Sunny?
Why not Sabo, who has already been portrayed as a rival of Lucci's in film gold? In fighting Lucci, Sabo will reveal that he is still alive, putting him at risk to be targeted again by the WG. However, he will help the SHs and vegapunk leave Egghead and move on to other things.