I once posted a ttrpg based in Middle Earth I'd love to craft. Central to it would be the wanderings of Saruman during the years he took up residence in Orthanc. Because of that, I drafted some fan-fic origins. They are PURELY speculative, but I'll leave them here. Perhaps they will spark conversation:
My thoroughly elaborated backstory is that Saruman, the only of the three later Istari who volunteered to leave Valinor, I like to think has a bit of chip on his shoulder as he was the only one not selected for the task (wonder if there's a little foresight there). So he is, maybe more than the other two, incredibly determined to fulfill his duty to the best of his ability. As such he seeks out those who have gone before to learn from, namely, the two blue who went forth in the Second Age.
There however he does not find two wizards united in purpose. The first, the one he knew as Pallando, has, in his quest to help all life in the East, spent much of his time with trees; the long inhabitants of that region whom he has learnt much from. The floral equivalent of a later Radaghast. The other, once Alatar, in his quest to cause division amongst the servants of Sauron, has overtime become directly set against Sauron as a rival mystic lord, followed by a spreading cult of believers. He has used the palantir he brought from Valinor, intended for communication across the seas, to instead peer at days not yet come and thereby granting him powers worthy of diefication in the minds of those swayed away from Sauron and to his course.
In the years that passed Alatar, renounced his god-kingship and 'retired' after seeing the devastation caused in his name. Saving a child from a genocide wrought by his followers, Alatar become nothing more than a solitary fisherman. He fell in love and they raised their son. Though his followers grew, despite his absence. Following their influence to its source, Saruman found Alatar. He became aggrieved to see one of his order fall so greatly and tries to reason with his friend, to come back to their united mission. Alatar attempts to explain to Saruman that this is in fact their mission. This is opposite to darkness, and a far better stance than that he held before. The simply everdyday acts of love can fight back against forces of despair and destruction. In the meantime, Pallando found the palantir. In it, he saw the death of the trees at the hands of Saruman. Lost to his own cause, Pallando sought out Saruman.
Pallando finds them and sees only failures, those who have or will cause destruction in Middle Earth. Saruman is forced to strike down Pallando, one of his own order. A terrible path is begun. And Saruman picks up the fallen palantir. He plans to cast it into the oceans. However, at the moment of casting it into a depth where it shall never be found, Saruman, seeks to perceive how to destroy the growing dark power of Sauron. In the palantir, he glimpses visions of great machines and forges mastered by himself, a lidless red eye blinking out and a people of small stature toiling under his own supervision. He struggles with the choices he has made to defeat one of his own order but also the images he saw. It seems that to defeat Sauron he must turn to machinecraft. And perhaps the Little People, should he find them, may play a roll. But his mind ever turns to the memory of the power of the palantiri and how, with another in his hands, he alone may succeed in cleansing the land of darkness. Thus, an obsession to find one of the remaining seeing stones in the West is kindled. Saruman takes his studies to Minis Tirith.
This is entirely fan fiction but I think an interesting 'origin story' for Saruman and a perspective on other ways the Istari can 'fall'.
This is obviously Second Age stuff. But, the idea of the Istari entering the East as Sauron does and having them almost act as a detective duo hunting him out, having seen signs of his manipulation is interesting to me. Having sequences of them kind of playing PI, since they could be this early-trial mission of the Istari and have no precedent for what their role might be. And in that, we can see the beginnings of differing interpretations of what is good about Arda and what works in opposing evil. Leading to a division between them by the end of the season. Like True Detective with wizards. So if we do catch up with them MANY series down the road, it'll be a real shock to see what roads they've gone down.