Another theme could be friendship. The dragon could become Ichigo's new friend or ally. Their relationship might be explored, how they communicate, trust each other, and fight together against common enemies. It might also show how Ichigo's existing friends interact with the dragon.
One 'ichigo has a dragon' fanfiction might be about Ichigo discovering a hidden dragon within his spiritual power. It could involve him learning to control this newfound power and using it against powerful enemies in the Bleach universe.
Uryu could also be a main character. He might be initially skeptical of Ichigo's transformation into a dragon god but then come to respect and even rely on his new powers in battles against common enemies. His Quincy abilities could contrast with Ichigo's dragon god powers, creating interesting interactions between them.
One possible analysis could be the unique power combinations. Ichigo already has his Shinigami and Hollow powers, and adding the White Dragon Emperor's abilities would create a really interesting and complex power dynamic. It might also change his relationships with other characters in the story, like how his friends and enemies perceive him.
Fans of Ichigo from the original series would probably be interested. They'd want to see a different side of the character. Also, people who like dragon - themed stories would be attracted to it.
A common plotline is the training arc. Ichigo has to learn how to use the White Dragon Emperor's power effectively. This usually involves some sort of mentor figure, either from his own world or the White Dragon Emperor's realm.
Survival is a big theme. In many 'dragon hollow ichigo fanfiction', Ichigo has to fight against various enemies with his new dragon - associated powers and Hollow side. Also, friendship or unexpected alliances are common themes. The relationship between Ichigo's Hollow form and the dragon can be seen as a form of friendship or a strategic alliance in some stories.
It could be a fanfiction that delves into the power dynamics. Since Ichigo has three zanpakuto, perhaps it shows how his power has increased exponentially. It might also be about the training he had to go through to be able to handle three zanpakuto, and how this changes his role in the Bleach universe.
Well, in the context of fanfiction, it might mean that Ichigo in this particular fanfic has some sort of all - powerful ability. It could be a really interesting take on the character, making him super strong or having some unique powers that are not present in the original source material.
One idea could be that the female Zanpakuto has a unique personality. For example, she could be sassy and constantly tease Ichigo while also being fiercely protective of him. In the fanfiction, she might have her own backstory, like being created from an ancient power that was sealed away for centuries until Ichigo awakened her.