I think it would honestly be nice to have an episode/or in manga that shows what Edo Tensei was first used for? As well as to find out how it got so famous?, Who was the first one reanimated? What purposes did it serve in the first shinobi world war? How did Madara know the handseals to it himself? What drove Tobirama to want to bring the dead back to life? How did he go about creating it? Do you think there should have been something that could shed light on Impure World Resurrection?