So I was standing there in the kitchen, working on a batch of my specialty meatloaf, when suddenly, it hit me. Something was amiss in the Bleach universe, and it definitely wasn't Aizen's Gaga-Butterfly transformation. So I decided (five or so minutes ago) to write a blog about the thought, before I lose the details that formed the gist of it. I don't know how many people will read this, but I think that it's definitely something to ponder.
Let's start from way back in the series, when Rukia explained the premise of the Shinigami-Quincy War to Ichigo. She claimed that the Soul Society's reasoning was that killing Hollows was essentially erasing souls from existence, which would throw off the balance between the living and the dead, leading to what would essentially be the destruction of the world. Assuming that whatever textbook she read this crap out of isn't the same one that said Vasto Lorde-class Hollows are the harbingers of doom (kidding), then we have no reason to believe that this isn't true - if the Shinigami hadn't did what they did, then the world would be screwed. Now, saving the world is all fine and dandy, but I smell a Menos.
Now let us look at the structure of what we know as a Gillian, or Menos Grande as it was first called, which was ironically introduced just a chapter or two after Rukia's dramatization of historical events. As per the definition of a Menos, this one Hollow is actually composed of hundreds of others, that joined together through some orgy of cannibalization. Wait, what? Obviously, each of those Hollows was once a human soul, and as far as we have been told, once a soul is completely devoured by a Hollow, it can never pass on into the afterlife. So essentially, the existence of that one Menos Grande means that at least a hundred humans were screwed for an eternity. As far as we've seen, there are many of these Gillians within the depths of Hueco Mundo, seeing as they are the most common form of Menos. That means that thousands upon thousands of human souls turned-Hollow can never pass on into the afterlife. Sound familiar? But it doesn't end there.
As we all know, Hitsugaya described two more types of Menos - Adjuchas and Vasto Lorde. Given by what we know from Grimmjow's flashback, we know that a Gillian must eat several Hollows of its own kind for its power to progress. This of course means that the aforementioned thousand human souls (or their remnants, at least) are now contained within a single being. Grimmjow stated that to prevent oneself from reverting to a Gillian, an Adjuchas has to eat Hollows on a regular basis, Hollows that are also Adjuchas.
Let's hold up and do the math:
1 Gillian = At least 100 Hollows = The same number of Human souls
1 Adjuchas = Judging from that manga panel, let's say 10 Gillians for the heck of it = 1000 Hollows = 1000 Human souls
Pause here, and look at the scene where Grimmjow's Hollow gang tells him that they cannot become any more powerful than they already are. Yylfordt Granz tells Grimmjow that their total Hollow hunt rate is at 3000. Mind you, the rules are that those Hollows had to have all been of the Adjuchas class, so that is already 3 million Hollows that have been erased from existence, along with the human souls that they once were. This does not even take into account the other Adjuchas-class Menos that must have had comparable hunt rates to reach their level, or even the Vasto Lorde-class that have exceeded them. We're talking about millions of human souls that cannot pass on to Soul Society or reincarnate. For even the weaker Fraccion in Aizen's army, that's a chunk of human souls that can never be accounted for again. Who knows what lengths somebody like Harribel had to go to reach her level?
Now, even so, my math has some flaws. I am not taking into account that for each of those ordinary Hollows to have joined together to become Menos in the first place, the void in their soul had to have been too large for human souls to fulfill, meaning that they've already eaten at least one human soul. Even if each Menos component only ate one soul apiece, my grand total of 3 million (not in single Hollow mind you) would be doubled to a grander total of 6 million. Imagine how much higher that number can go if we knew how many humans each Hollow ate.
In conclusion, Grimmjow's gang alone comprised of over 6 million ordinary Hollows in total, with each one of those corresponding to a Human soul. As we know, even if a Hollow that has eaten other souls is purified, those souls are still lost forever (i.e. Masaki). Now, what damage could the Quincies have possibly done to the balance of the universe compared to this mess that was already going on in Hueco Mundo? Over a period of perhaps centuries, the thing the Shinigami were trying to prevent was already being propagated by the natural evolutionary behavior of Hollows. For balance to continue to exist, there will never be a shortage of Hollows - so what happens as the number of lost Human souls increases? Will the world end, as Rukia put it, or was the Shinigami's reasoning just some BS they pulled out because they didn't want the Quincies to cramp their style?
I apologize if this blog was too long, or if my logic is way off, or if my facts aren't straight. However, I would greatly appreciate the thoughts of anybody who has the time and patience to read through this.