Since Stella is not familiar with the traitor looks but it is shown that he is on Egghead for a long time (at least since the start of the CP agents disappearance).
I think the traitor will be a self-made (8TH) Vegapunk that created it’s own body by using the man-made organs that Robin and Chopper saw back in chapter 1075 since Atlas said that she can replace her body parts whenever she needs, which means that if you have Stella’s mind it is posable to create a body even Robin was asking Atlas if those organs were Vegapunks.
This would explain how the traitor was able to bypass all of the security on Egghead, because he is Vegapunk. It would also explain why he didn’t kill the Stella Vegapunk, it is because he’s going to steal his antenna to absorb all the information from Punk Records.
Chapter 1077, title is ” You should have put it together sooner” what if thats Oda telling us its been Vegapunk all along.
Also he is the one that gave commands to the Seraphims, so he is above Sentoumaru in the hierarchy to override his command which means that he is either a Vegapunk or one of the Five Elders, but the Five Elders were not on Egghead for that long time to capture the CP agents. So the traitor will be one of the Vegapunks – the 8th Vegapunk.