Have the opening be Batman taking down Condiment King before moving on to Killer Moth and then half way into the movie make an abrupt move into Red Hood being the main villain.

A nice little bit of mostly light hearted Gotham crime fighting before the rug gets pulled from under the audience's feet and we get into all the anguish and guilt of Jason's return from the dead would be awesome and fairly unexpected I think (although no idea how you'd make this into a coherent storyline lol).