It is doubtful that it would change anything relating to the first final days as by the time you get there, hermes had already sent out all the sisters. They had already found every dead planet. Even if you could have stopped the final days from ever starting, it would not have mattered for the timeline you came from. You would have just created an alternative timeline. Additionally, non of the other ancients would have allowed you to kill hermes. Doing that would also have doomed that timeline as his knowledge over the celestial currents allowed the ancients to shroud the planet with the help of zodiark.