well if you dont know then thats why Psi=Idea
as for there being another influncial being besides fate...part of me agrees that it would be cool if there was a "Thought" or someone else but when flora talks about the astral realm and Idea, she speaks pretty much as if there is only one. Also the reason why I'm pretty sure that Guts is under Idea's control, is that he represents the same human emotions that helped create Idea. Griffith is a representation of a human's ultimate desire for power. Guts is in a way symbolic for human's desires of revenge, as well as lust/love (but in a way so way griffith. griffith <3 guts

). whenever the Godhand meet him, they revel over how strong his feelings are. they could litereally eat him up

.
and i disagree with Wikipedia

. but i do think that Berserk is still open for the introduction of the counterpoint of Idea/Godhand. Muira has left it open so I'm not going to rule it out. The abyss is a dark and deep play that many have not explored, Flora may just not know about it, like a lot of stuff. And Sandman, would surviving the eclipse not just make Guts an even more complete representation of the rage and desire for revenge humans feel.
I wonder when/if Guts is just going to become a big beast wolf guy (like from his evil dream when he is fucking/tearing casca apart) like SK turned into a "SKull Knight" though honestly his persona, if it looked like that, would look pretty dumb