We have Griffyn612 theory that Mac is a transubstantiated Raphael. Considering the same evidence that Gryffyn puts forth for Mac to be Raphael, I'll put forth for him being God.
So, do we have evidence that precludes Mac from being God? What does it mean to be God within the Dresdenverse. Definition of DF God: ?.
We know that Mac creates "God's brew". And He is often described as downright Angelic.
If Mac is indeed some projection of God, then it makes more sense that he was more of a target in Cold Days with the Outsider attack on Demonreach than we believed. And Harry brought him there. Mac couldn't compromise mortal free will, therefore he followed. The attack on Demonreach with Mac upon the island then isn't possibly as much about destroying the island, releasing the sleepers, etc but doing away with God's projection within this reality. I don't think it would really 'hurt' God so much but it could cause a wrinkle in the balance of power for a moment. We now know per WOJ that God has commanded Outsiders to remain outside of Creation, outside of the Sandbox he has given us. However, he has given creation this sandbox, given mortals free will, so if we are going to wreck this creation by bringing in the void (Outsiders), then that is on us.
A: Almighty isn't really about determining the order of the universe. He isn't a GM. He made us a sandbox game and then let us decide how to play it, and mod it.
Now He's already told those forces, 'stay out of my sandbox' and they do. But He's also gives us the sandbox. And if we want to invite them in to screw it all up, well. The void is still there. Waiting.
I think even if God has settled on allowing Us to choose our Fate, I wouldn't put it past him to place a transubstantiated form in play of himself. And who better for this form to be than a bartender making God's brew, interacting with a Starborn that will likely be the deciding factor in the Fate of the Universe/Multiverse.