The time travel of Archer can also be a way to resolve long - standing plot issues. If there is a mystery about Saber's past that has been plaguing the story, Archer could travel back to that time to uncover the truth. This could then lead to the resolution of other related plot points, like a feud between two kingdoms that was somehow related to Saber's origin. It could also create a ripple effect that changes the entire power dynamic in the story world.
His time travel can also introduce new characters or storylines. Maybe he travels to a time when a powerful mage existed who could help Saber in her journey. By bringing this character into the present (or past, depending on how the time travel works), it would add a new element to the plot and create new relationships and conflicts. Another way it affects the plot is by changing Archer's own character development. Through seeing different versions of Saber in different times, he might grow and change in ways that wouldn't have happened without the time travel.