I'm really interested in trying to get more information about Void, and one angle I haven't read much about is this: does the amount of people sacrificed, and their strength, influence the power of the resultant godhand member?
There definitely seems to be some kind of correlation between sacrifices and power, since Slan states in chapter 82: "It's ironic though. The stronger his life force and the greater his anguish, the more they become precious bread for the new life of darkness". From this we can at least deduct that a strong sacrifice makes the new member stronger than a weak sacrifice.
Now the question is: shouldn't this mean that Void is much, much more powerful than Griffith currently is? After all, he sacrificed not just a band of mercenaries (who have some very strong members, albeit only few due to the year before), but an entire kingdom. I do think the average sacrifice was much weaker for Void (as they were most likely not warriors, but intellectuals), though it's difficult to say since we know very little about his eclipse. But nonetheless I definitely think there is some correlation here.
This of course leads to some interesting possibilities for what Griffith is currently up to. Is he planning to somehow ascend further by making another, much bigger sacrifice? Do the godhand members have a hierarchy which he is trying to climb (almost certainly)? Could he be trying to surpass the Idea of Evil itself?
One thought about the ending - Miura said that Void is key. Are we 100% sure that this refers to Void the God Hand member? If I understand correctly, some cultures have void as the 5th element in the classical water, fire, earth and air cycle - which maps to the 4 cardinal kings suspiciously well, who are one member down compared to the God Hand. It could make a lot of sense that they lent Gaiseric their power to unite the people, but he abused it and hurt his people instead. The evils of humanity, too concentrated for the first time, created the Desired God. He influenced the kings to create a 5th member, supposed to guard against the problems of Gaiserics Kingdom, and chose the man who never stopped proclaiming Gaiserics sins. But after his ascension, he did not join them, as he was angry about the torture he's been put through, and lost his connection to humanity - only being fuelled by hate for Gaiseric. Since then he's been creating the first God Hand, with Femto being the completion. The four kings regret their actions and are helping humanity as best they can since then. The end goal of Berserk might just be a 5th cardinal king, born from the ambitions of the Griffith to ascend, but instead having ascended Cascas and Guts child to the role of the promised Void.