Modifying shadow depth pass

Background: I would like player objects in my game to not cast shadows on themselves, but recieve other shadows and cast shadows on other objects. I am able to achieve this with multiple lights and layers, however it is redundant as I must render all the non-player objects to a depth map twice.

I think it would be more efficient to render all shadow casters other than the players to the depth map, copy that map for use in the player shader, then render the players to the depth map for use in all the other objects' shaders. This way every object must only be rendered in the depth pass once.

How would I go about doing this? Can I use command buffers?