Batman's plans are individual and specific, exploiting the particular weaknesses of each of his friends.
Uh, because they were intended to, "in case one of them went bad." He never made a plan to take out The League, he made plans to take out Superman, Wonder Woman, Martian Manhunter, Aquaman, Flash, Green Lantern, Plastic Man, etc. Because he knows the League works best together, and he believes together they can beat anything.