I don't really understand your point, but if you mean to address why Tobirama didn't release himself from Edo Tensei when fighting Sarutobi, it was likely due to the fact that Orochimaru didn't give them any free will. Kabuto pretty much let Madara act on his own. Since Madara wanted to test his abilities and kill everybody anyway, there was no real reason to waste the energy trying to control him. The Hashirama and Tobirama, on the other hand, didn't have any intention of fighting Sarutobi. When they were first summoned, they just stood around talking. They couldn't move without the sealing tag completing the Jutsu, but they also weren't nearly as excited about killing their comrade as Madara was about killing the Kage.
As for Kishi knowing the plot in advanced. Many aspects of the story are kind of predictable if you look back through the series. Tobi and Kakashi having similar MS abilities foreshadowed Tobi being Obito. Bringing Orochimaru back by breaking a seal foreshadowed bring the Hokage back by breaking RDS. Even look at the Chunin exam fight between Naruto and Neji. Neji gives a whole speech about how Naruto couldn't possibly be Hokage because people are destined to be Hokage. I think this is kind of ironic, because Naruto is kind of destined to be Hokage. He is the son of a former Hokage, student of one of the Sannin (who was a student of a former Hokage and a teacher of another former Hokage), is a Jinchuriki, is a distant relative of the First and Second Hokage, etc. And finally, RDS makes the perfect plan on how to bring back all of the Hokage at once. First, since their sealed, it eliminates them from Kabuto's arsenal of ET zombies unless he knows how to break the seal, and it puts their souls all in one place. Plus it opens the door for Orochimaru to return to full power (either as a villain or a reformed criminal) and for Naruto to get a huge power boost (with the Kyubi chakra sealed by RDS potentially returning all of a sudden).
