There's two directions this can go,
Anakin is our first Empire GL and they paired Republic with Empire to represent order. They will follow up with a Seperatist and a Rebel to represent Chaos.
The second direction, is to have Anakin Skywalker Fallen be a DS GL with limited Separatist and Sith synergy similar to Kenobi. More of an emphasis on Sith than Separatist.
Sidious was the mastermind of the CIS with Dooku serving as the figurehead ala Snoke to the First Order. As Sidious' apprentice, Vader would be a Seperatist.
Maybe negative synergy with Seperatists similar to Grievous. He damages or weakens them to build his own power.