Ichigo Kurosaki is hailed as one of the strongest characters in the Bleach series. Half shinigami and half Quincy, his hybrid nature and immense power made him an ideal candidate to become the new Soul King. It was an idea that the creator of the series, Tite Kubo toyed with but never implemented.
The Royal Guard had plans to turn Ichigo into the new Soul King after the previous one died. This would require killing Ichigo and turning him into the new Linchpin of Existence, stabilizing the balance between Soul Society, the Human World, and the realm of Heuco Mundo.
The Royal Guard planned on making Ichigo the new Soul King in Bleach
Can’t Fear Your Own World is a series of Bleach novels created by Ryōgo Narita, under the supervision of Tite Kubo. It is set in the aftermath of the Thousand Year Blood War and captures the turmoil within the Soul Society following the war. The light novel also reveals that Ichigo was supposed to be the Soul King.
According to the novel, the Royal Guard, also known as Zero Division had plans to sacrifice Ichigo and turn him into the new Soul King once Yhwach killed the former during the Thousand Year Blood War.
Leader of the Zero Division, Ichibē Hyōsube, was in favor of sacrificing Ichigo, with the Captain-Commander of the Gotei 13, Shunsui Kyōraku also being aware of the plan and being on board with it.
However, with Yhwach being defeated, the plan didn't come into effect and Ichigo was spared from being sacrificed and sealed like the previous Soul King. Without Soul King acting as the Linchpin of Existence, the Soul Society, the Human World, Dangai, and the realm of Hueco Mundo would all collapse into one, with the balance between the realms offsetting.
Thus, had the Soul King fallen to Yhwach, someone would have to take his place. Ichigo was born a hybrid with immense power, and he was a perfect candidate to become the new Soul King, according to the Royal Guard. However, Bleach's creator, Tite Kubo, decided to go against this development for the protagonist.
Who is Soul King?
Soul King is a godlike being who acts as the Linchpin of Existence, stabilizing the balance between Soul Society, Dangai, Heuco Muno, and the Human World. He's also the ruler of Soul Society and lives in the Soul King Palance, which is situated above the Soul Society in a separate dimension.
The Soul King remains within the palace, sealed in a barrier, and is protected by the Royal Guard, also known as the Zero Division. He doesn't govern the Soul Society or interfere with its problems and acts more like a symbolic figure whose only job is to stabilize the balance between realms.
Conclusion
In conclusion, Ichigo Kurosaki was considered the perfect candidate to become the new Soul King, if the former Soul King died during the Thousand Year Blood War. This was a precautionary measure taken by the Royal Guard. The plan was relayed to Shinsui by Ichibe.
In the end, Ichigo wasn't turned into the new Soul King. He managed to avoid the fate of being sacrificed and sealed in a barrier as a catatonic God who was only there to maintain the balance between realms.