TLDR; Ichigo is a perfected Hōgyoku because he has a combination of all different kinds of reiatsu in him and has wish making powers he doesn't realize.

OK, so hear me out:

I was thinking about how Ichigo is in such a unique place as a character in comparison to everyone else in Bleach, even in comparison to Aizen. Aizen and Kisuke made the original Hōgyoku by taking a massive amount of souls and then using those souls to create the first few Hōgyokus. Even when Aizen was making White, he was also using his experimentation to expand on how one could manipulate souls of shinigami to create a hollow, as it consumed more shinigami's its power grew and then eventually encountered Isshin and Masaki, dying against Masaki while imbuing her with its hollow powers.

Story goes as we know and White transfers to Ichigo, making him a combination of Shinigami, Hollow, Quincy, and Fullbringer, since all of those are tied to his parents, the fullbringer part being born of his mother surviving a hollow attack. This already makes Ichigo a unique being thats about as close to the Soul King as possible at his core.

Cut to Ichigo as a teen, he encounters Rukia and gets her Reiatsu implanted in him, which awakens his Shinigami powers and stirs up those Hollow Powers a bit, because they're connected. Story goes as usual, we get to the part where he has no powers, unlocks his Fullbringer abilities, and then loses *those* to Ginjo, eventually ending with ALL the captains and lieutenants of the Gōtei feeding parts of their reiastsu into him, unlocking his powers all over again.

Here's the thing that took me forever to get to: What if it was that moment that turned Ichigo into a perfected Hōgyoku? We know Hōgyoku's sort of do their own thing according to their will, but they're made from the combined reiatsu of a number of souls, including Shinigami souls. Now, White and the original Hōgyoku were made from of souls, but none of those souls were as powerful as the ones that imbued some of their power in him at that time. Sure, it wasn't their full power, but Isshin states that Captains have so much power that they need to focus their reiastu in a way that doesn't make their Zanpakutō the size of skyscrapers. Even with a fraction of that amount from the Gōtei captains and lieutenants combined with Ichigo's unique body give him the wish-like properties of the Hōgyoku. His wish being: I want to be a Shinigami again.

So we get Bleach as it is up to that point and for all intents and purposes Ichigo is the perfect shinigami but isn't aware of his history as a Quincy and can't take that into his wish, so its not till when the TYBW that he can start incorporating that.

There are so many weird circumstance around Ichigo's power and how he gets his Bankai back after Yhwach comes back, which can feel kind of cheap and like wish fulfillment, but what if its like that because it is and Ichigo just doesn't realize it.

Aizen and his Hōgyoku were separate from the start so when they became one maybe it wasn't a perfect union, but Ichigo being his own Hōgyoku could be a reason why he stands in such a unique place at the end of the Manga and that could be a part of why his kid has such a unique set of powers as well, maybe their like their dad is and in some way a Hōgyoku, but as kids the power of making wishes just hits different.

Obviously: This is just a random thought that popped into my head, but has anyone thought of this before?