I feel like we'll be playing as Theo since in the description it says, "You aren’t just here for the paycheck. You have a greater purpose here…stay the course. One goal, four ways to end it." And in the lore document it says, "You take the job, whoever you are. There’s a lot you don’t know, and a lot you don’t understand. You’re here with a purpose, and you cannot turn back. Stay the course, and finish what he started. If this is correct it's referring to Theo finishing what Jack had already started before the facility collapsed.