On a beginning note, before I get into this, I'm not kidding about this.
I think for one game four fans are picked to call the offensive, special teams, and defensive plays for the game. Each quarter the fans alternate, and one fan sits out one quarter each. You could give playbooks to each fan 2 weeks earlier, so they can study the plays, and think about what they'd like to call. This could show how much fans know about football. Of course you'd have to prove (in someway) that you would know what you were doing as a coordinator. I bet you that would sure get interesting.