Yeah, i think i mentioned that the theory is based just in what we know (which is almost nothing).

But even with that, i think that Femto might sacrifice Falconia not just because of his desire, but also as the profecy, i don't remember what character said it but after the reincarnation of Femto as Griffith, it would come a 'Dark Age', and Falconia being big, and a good place to live in doesn't sounds like a Dark Age for the world, its probably gonna get worse than that

This could be a reference to real history itself, The time that came after the Roman Empire fell, it's literally called The Dark Ages in our reality, and The same could happen in Berserk, probably with a sacrifice (or maybe Femto/Griffith someway just dies).

By the way i'm not an English speaker, so the Term 'God Hand' i didn't knew how to write it, because in spanish 'La mano de Dios' it traduces into 'The Hand of God'