So...!
The theory or fact until proven otherwise goes...! Aizen, has been at this a little longer than I thought. My thoughts on Kisuke being the fault of this was wrong. It was in front of me the whole time.
Three shadowy figures, Aizen, little Gin, and Tousen working on the formula to create a hollowification of a shinigami. Check the highlighted box, it didn't work on a normal soul so whats next? A shinigami of course... (Always test your formulas on something else before yourself right?)
So they had to create a diversion to get the captains sent outside of Seireitei. But how could they get the captains to stay until they were ready to carry out their plans?
Only somone from his own squad could know such a thing..(The relvance of the #10 not getting into details)
Seems like he wanted everyone there at a specific time...?
Betrayed!?
Of course not just...
So Aizen created the virus that turns the shinigami into hollows, and it was administered by Tousen!!
Now to the theory:
Aizen soon learns although they took the form he wanted them too, they are unable to control the powers, and remain a violent untamed force. He then aborts all intrest in that idea, and this is where Kisuke comes into play. Kisuke then developed the Hogyoku, to then dissolve the boundary between their hollow forms and Soul reaper forms(Allowing the fight between you and your inner hollow to take place).The Vizard leave, and Kisuke trys to cover it up by trying to destroy it, but he can't. If someone were to find the hogyoku, many questions would be asked, so he developed the untracable gaigi in an attempt to hide it. Once Aizen learns of the Hogyoku and how eaily it created what hes been working so hard to achieve he then took action. WELCOME TO WHERE WE CURRENTLY ARE IN HM!