Edo Tensei might have been preventable by a younger Sarutobi hah. It was already preventable he prevented Oro from bringing back the fourth easily enough and that was because he thought he would have been able to handle Oro and the other two hokages. He himself said that he stopped him from bringing back the fourth because he knew he wouldn't have been able to handle him.

So it had nothing to do with it not being preventable because it was. The problem was that he didn't realize just how strong Oro's jutsu was, he thought that simple techniques that would kill or destroy a normal human being would have been able to work on them, like using the explosive tags for example. He later realized that the only way to stop them was to effectively remove the souls from the bodies and then seal them so they couldn't reform. At that point there was nothing else he could do besides Shiki Fujin.

The point of that battle was that he had to fight his teachers so that wouldn't have changed and as I said even if he was younger the only way the outcome would have changed would be that they both would have died.