There could be a lot of uses for this, but the big one for me is animating the face. Maybe a texture has its own layer system (ideal) or even just being able to keyframe one skin to another in order to swap out expressions or clothes or something. Additionally, it'd be great to have an expression library to contain all the expression options. Hopefully I'm explaining this well: Laika uses the replacement process for their films (Kubo, Coraline, ParaNorman, etc.)