After the somewhat recent flashback to explain Urahara's past, I went back to watch the start of the Arrancar arc. In the fight between Ichigo and Privaron Espada Dordonii, he mentions that he "knew Aizen would cast the original Espada aside once he unlocked the power of the Hougyoku". The impression given by Soul Society in their briefing of Captain Hitsugaya was that if Aizen allied with 10 Vasto Lordes then he would be very powerful. They then go on to dramatically show Aizen asking Ulquiorra to present a report to his '20 brothers and sisters', establishing that he had obtained more Vasto Lordes than needed by Soul Society estimation.
Setting aside that the Hougyoku is needed to make the King's Key:
If Espada existed before Aizen started making them with the Hougyoku then why did he need it to create them in the first place? Was so that he could customize his army? Ensure he had loyal, grateful followers?
Which Espada are original and which are created? Can we assume that Aaroniero wasn't created because he's a Gillian? Isnt the value of the Hougyoku that it can turn Adjuchas into Vasto Lordes?
If Grimmjow ate his Adjuchas companions (as they ask him to do in the flashback), how do they reappear as his Fracción? Is this the Hougyoku?
Any answers or insight are appreciated :D.