Can you expand on this? I don't see the issue. Sure the GM isn't mentioned but it should slot right in. We know from Demon Storyteller's Guide that the machine isn't earth bound.
This is, obviously, my own personal opinion. As such YMMV.
The primary issue comes mainly from the primary decision that hast to be made about any individual IM game. "Does the 'veil' of secrecy surrounding the supernatural still exist?"
If the answer to that question is Yes, well then the God Machine and Demons fit in just as much as they fit in with WoD in general.
However, if the supernatural in your world is exposed, so is the very presence of the God Machine. Remember, a central conceit of GMC is that the God Machine actively covers up supernatural occurrences that might attract to much attention for fear of itself becoming exposed as a result. The idea that the God Machine can actively hide, and that Demons aren't just going to expose it when literally every other supernatural is on display by exposing themselves and dragging the gears and workings of the God Machine into the light, just breaks my Suspension of Disbelief. If Onyx hadn't been quite so insane with the God Machine (IE: the fact that it's got Infrastructure and Machinery basically EVERYWHERE, with most of the obvious stuff hidden behind what amounts to "Wards of You Cant See Me!") then it could have worked.
But as is? How does the God Machine fit into IM? As a sort of " 'evil' Culture Mind", it can definitely work. In the Storyteller Guide, we see a whole city that the GM has basically regressed out of normal reality, slowly pulling it out of the world and into its own little pocket dimension. To quote a relevant passage, " They do not see it for what it is, nor can they see past the veil hiding the gears or agents of the God-Machine. Instead, they have a sense of it, an intrinsic knowledge that Mechopolis is a living city and they are all pieces and cogs within the greater whole. People live their lives knowing their god has a plan for them, and they serve it without fail. They willingly go each day to tend and maintain Infrastructure, build new machines, and submit to experimentation — all in the name of their glorious god."
But, in order for the GM to be Evil Culture Mind, it can't be the GM as we know it. It can't be capable of just traveling across all of time at a whim, it can't have it's gears and infrastructure everywhere, it cannot be the 'Real' God Machine. Because if it has these powers, then why hasn't it used them to conquer the whole of existence? Unless, that isn't in its nature, but as we've seen in GMC and Demon, all that the GM seems to care about is growing in power. It doesn't care about humans, or vampires, or even whole cities, unless they can serve a purpose. When faced with a Meteor that will strike the earth, it doesn't thing, "omg, all those humans are going to die!" it thinks, "Unacceptable. This strike will destroy 90% of my infrastructure on this planet."
And so, we come to the main 'thing' of it. The reason WHY the God Machine and Demons don't "fit" Infinite Macabre is, "This product is written with the second assumption in mind. We want the monsters out in the open because it creates more fantastical conditions. Instead of having to worry about bizarre-faced aliens wandering the market bazaar or space-dock, we get to have pale bloodsuckers, porcelain Prometheans, and the truly bizarre Lost rubbing elbows with humanity. In this mode, the monsters become the aliens so frequently seen in the various iterations of space opera." And you want to know what isn't fun? Spy Games going on out in the open. Which is what Demon is all about. As such, they just do not fit because I cannot reconcile them with the very theme of, "supernatural exposed" that is a major conceit of IM.
I don't play / run Infinite Macabre to hide supernaturals. I do so to explore things that just can't / aren't explored in basic WoD, which includes a fully exposed supernatural world.
