This is according to the game’s live producer Lathieeshe Thillainathanm, who revealed the news during an Ask Me Anything (AMA) session on Reddit. He said that the team is currently “writing the full single-player story again with [Aiden’s] personality”, adding that Pearce will be “integrated into all the original cinematics”.
Thillainathan also confirmed that players will be able to run through the main campaign as Aiden without having to complete the DLC first. “Aiden can replay the full game and will have a dedicated DLC with Wrench. You don’t need to finish the DLC to play as Aiden in the single-player story,” he said.
Aiden will arrive in Watch Dogs: Legion post-launch, via a DLC that will also feature three other playable characters: Wrench from Watch Dogs 2, an Assassin named Darcy and Mina, who wields psychic powers.
It is currently unclear if the other three characters will receive the same treatment as Aiden, with a rewritten campaign arc. However, Thillainathan did confirm that all four post-launch characters will be fully customisable in both single-player and online modes. “Once they are on your team, you can customize them as you wish. Can’t wait to see everyone’s version of Aiden and Wrench,” he said.