Re: Nagato and Danzou
Here is a couple things you could consider.
One thing is that Kishimoto is just like the rest of us humans, and merely forgot that detail.
Second thing is that it could have been part of the plot, so that Sasuke could attack and kill him, bring his hatred and insanity to a whole new level, plus deteriorate his eyesight so that he'd take Itachi's eyes.
Third thing is that we forget that Danzo is a capable fighter. Had he had Shisui's eye, I don't think he would have lost to Sasuke. Though I don't denounce Sasuke's win in any way, shape, or form, it could possibly be the truth. Then there is Fu and Torune who were beaten by Madara's teleportation technique, which Pain doesnt have. There are also many other talented members of root. So if you think about it, Danzo himself could take on POSSIBLY 2 or 3 bodies, plus he probably had some intel on Pain just like the rest of Konoha. Fu and Torune may be able to take out Animal and Preta Path, or Naraka Path (the one who was taken out by KONOHAMARU). We don't even know who else in root can fight well. Danzo wanted to become Hokage, but the other reason Kishimoto didn't put him in the fight could have been because it would have been unfair in Konoha's favor.