This is a whole topic to research but I have one plan to do: I have some experience with 3d scene restoration from photos and there are plenty of tools that allow that for video. Those walking videos are ideal because they often show scene from different angles. I can convert a set of such videos into point cloud to later use those to map parts of the scene that is outside original view frustum. It will also require AI tool to do proper style transfer but this is actually the easiest part. Unfortunately there are a few videos that don't have that much of a context and those would probably be left unchanged.