I have a strong suspicion that this is going to end up being an experiment in interactive storytelling. ILMxLab has been developing games for a while now and the extremely generic way they described the protagonist during the presentation is what you’d do if you want the viewer/player to assume that role.
Netflix already has a couple of interactive experiences with Black Mirror: Bandersnatch and Minecraft: Story Mode. So I could see Disney+ wanting to experiment with it as well.