It could also develop in an unexpected way. Suppose the Inquisitor gets injured during a mission and Ezra finds him. Instead of finishing him off, Ezra decides to spare him. This act of mercy could make the Inquisitor question his loyalty to the Empire and start to have a more nuanced view of Ezra.
Their relationship could develop in a hostile way at first. The Inquisitor is tasked with hunting Ezra, so he would be constantly on Ezra's tail, trying to capture or kill him. Ezra, in turn, would see the Inquisitor as a major threat and fight back with all his might.
As they work together more often, they might develop a friendship. For example, Ezra could teach Leia some of the more unorthodox ways of using the Force that he learned from Kanan, and Leia could introduce Ezra to the broader political landscape of the Rebellion. This exchange of knowledge would bring them closer.
His relationships would change drastically. His bond with Kanan would be severed, and instead, he'd form new alliances with the Inquisitors. However, these relationships would be based on power and fear rather than the friendship and mentorship he had in the Rebellion. He'd also be seen as a traitor by his old friends, which would add a layer of guilt and isolation to his character development.
In many fanfictions, the relationship between Ezra and Maul is a slow - burn one. At first, Ezra is afraid of Maul, given his reputation as a dangerous Sith. But as Ezra matures in the Force, he begins to understand Maul's motives better. Maul, on the other hand, starts to see Ezra as a kindred spirit in a way, as they both are somewhat outcasts in the grand scheme of the Force - users. This mutual understanding leads to a relationship that is full of tension but also has elements of cooperation and even a strange sort of friendship.
Their relationship could develop as they train together. Ezra would learn more refined Jedi techniques from Ahsoka. This would create a deeper bond of respect and mentorship.
Their relationship often develops through shared battles. As they fight side by side, they start to trust each other more. This trust then turns into a deeper connection.
Some fanfictions show their relationship evolving during times of crisis. When Ezra is in danger, Kanan goes to great lengths to save him. And when Kanan faces his own inner demons, Ezra is there to support him. These experiences outside of the normal rebel activities help them form a deeper, more complex relationship.
Ezra could develop by becoming more of a warrior. In a Mandalorian - centered fanfiction, he'd be exposed to their combat - centric culture. So he might become more battle - hardened and less reliant on just his Force powers.
A more complex storyline could be that the Inquisitor, who was once a Jedi himself, sees Ezra as a chance for redemption. He secretly tries to guide Ezra away from the path of the Rebellion, believing that the Jedi should stay out of galactic politics. This creates an internal struggle within Ezra as he has to decide whether to trust the Inquisitor or not.
Writers often start with their existing relationship in the show. They then build on it by putting them in new situations. For example, in a dangerous rescue mission where they rely on each other more than ever. This deepens their bond.
One possible storyline could be Ezra's struggle with the dark side. He might initially be lured by the power that being an Inquisitor offers. For example, he could be tempted by the ability to defeat the Empire more effectively but at the cost of his own moral compass. Another could be his relationship with the other Inquisitors. He might be an outcast among them, as he was once a rebel. Or perhaps he tries to use his new position to secretly help the rebels, creating a complex web of double - agent - like situations.