After playing around a bit with some VR, and having some experience with film, I had the idea to do an FMV game using 360 video. Unfortunately, I had a lot of lag issues with the inbuilt Unity video player, especially when going from shot to shot, and any attempts to mitigate it simply made the videos stutter instead of having a long load time. As a result, I got a trial of an asset store resource which solved the problem.
I've been working on a script and a shot list but they're still in development, however I've been working with some test footage to get the systems in place. I've built it around using Articy Draft to drive the branching, including shots to serve as an 'idle' while a choice is being made. The Articy Draft Nodes are linked to some footage using a scriptable object which also handles if there are any gameplay factors being changed. This includes manipulating post processing and a system where you can track whether the player 'saw' certain things happen by looking at their position at the relevant timestamp.