I also think Mike is the one that wants to be with Bob again on the telephone call that coop thinks he is having with Bad Coop. So maybe the grace from seeing the face of God has worn off or there is something more at play, if the arm evolved, Mike could have devolved so to speak.
Ages ago before the Secret History I had read the two books and seen the original series and movie. I was convinced from the scene where Bob feeds Leland's Garmonbozia up that spirits like Bob are familiars/agents working for the magicians, which eat the garmonbozia for power.
Bob is ordered by Tremond's Grandson to "fell a victim".
I think Bob is special because he is really good at gathering garmonbozia.
There does seem to be a collection of spirits that work together in the connivence store.
The woodsmen seem to be the lesser entities they generate fear by their presence and they feed directly on their victims.
Bob seems to be slightly more powerful and complex in action.
Mike / TMFAP seem to organize the lesser spirits and they have plans.
The magicians, Mrs Tremond and her Grandson eat Garmonboza and appear in TP physically. Still convinced Red is Mrs. Tremond's Grandson but that is another story.
I think in all of this Mike is pulling strings and I do not think the intended end is blessed by seeing the face of god. Also that could have been a lie. Time to rewatch the scene where he points.
I think the nature of Mike has never been explained and it can be even more confusing as it's entirely possible they changed their mind about it a few times as the story went on and took different directions than the ones they had anticipated (plus of course other circumstances like Michael Anderson's falling-out with Lynch that forced other changes).
The way Mike is introduced at first is that he's a spirit, very similar to Bob, possibly more powerful (he says Bob was his familiar, while he might be using the common meaning of the word, I read once in a book about Twin Peaks that in some mythologies that have highly influenced Frost's work that's also the name of lesser demons). Philip Gerard is said to be host to him, in the same way Leland is inhabited by Bob, which should mean that he's also a human being. And as a matter of fact we never see him in the Lodge until the very end of FWWM, he's always in our world and he's even able to get rid of Mike's possession when he uses haloperidol. Now I guess one might argue that his bond with Mike was stronger than the one between Leland (maybe because of the tattoo? Maybe because he tried to free himself of Mike by cutting the arm?) but that's just my speculation based on the fact that we've never seen anyone else possessed by Mike (while Bob has possessed Coop and Leland and he was trying to possess Laura when he was still with Leland). But again, a regular human being.
But things get more complicated. The show indicates that Mike was an evil entity, but then he saw the face of God, it changed him and he had to take off the arm with the tattoo (which probably was the cause of the evil in the first place). So he basically splits in two parts: Philip Gerard, still inhabited by the good version of Mike, and the arm, whose spiritual form is the LMFAP, who presumably is still evil. Then in the last episode the doppelgangers are introduced and there's also a LMFAP doppelganger, which should imply that the regular LMFAP is a good guy.
FWWM makes it even more confusing: while the One Armed Man and the Arm/LMFAP should be separated (and even conflicting) entities, they seem to follow the same path and at the end of the movie we even see them together in the Lodge, eating garmonbozia. Also, the ring is introduced and apparently those who wear it are wed to the LMFAP. What it means it's not clear, as they don't seem to be possessed, even though the arm corresponding to the one Philip Gerard is missing goes numb. The most likely thing is that their fate is in his hands (or, more precisely, in his hand) and Bob can't possess them, but the other implications are not clear.
Now season 3 brings some changes. Philip Gerard this far has been seen only in the Lodge, and not as a regular human being living in our world. I guess he's too old to keep travelling around the Northwest to sell shoes for a living and not everyone wants to spend retirement years in Florida, but he seems to be a full time Lodge resident and to have left the haloperidol years behind him. But also, we see he's definitely working together with the arm (now tree) and they're seemingly in with the good guys, while there's again a doppelganger who has other plans. All of which makes it nearly impossible to understand if: Mike can possess anyone else outside of Philip Gerard? Is there really any difference between the arm/tree and the One Armed Man? Is the One Armed Man really a man or he was just a spirit since the beginning? What does the ring exactly do and how those who wear it are wed to the Arm? What does it even mean to be wed to the Arm? If we can assume the arm/tree and Philip Gerard are both good, as opposed to the arm doppelganger, and they are pursuing the same goals, why did he cut the arm off and they split in the first place?
All of this to say, it's definitely difficult to give answers about Mike (and to some extent, about some other lodge related things): I guess you can say that they can possess even real people, not necessarily their doppelgangers (that was the case for Bob with Leland); and Mike's host should be Philip Gerard. But beyond those I guess everything it's up in the air. And even if we put together all the pieces that we have we might not draw a satisfying and perfectly coherent conclusion, because probably the role and nature of Mike has changed in the author's mind as they went on with the story, so we just have to wait and see if we get some more answers in the following episodes, or if we'll be left without a perfect explanation and we'll have to accept it as it is, pretty much how we do with the cowboy, the hobo and the old man in Mulholland Drive and the Mystery Man in Lost Highways.
I second the 'You're Awesome' comment. Great thoughts/summation!
I feel like the idea that MIKE is balancing the order seems the most compelling. His motives seem odd rather than good or bad this time round. He's trying to keep Dougie Coop alive but not actually trying to 'wake' or return him. It's clear that after 25 years, the doppelganger has to go back into the Lodge and swap. EvilCoop knows this and has been preparing his trick. But MIKE doesn't really seem to be trying to correct this. Unless....
Mike speaks to Dougie and guides him through Lodge visions. The arm/tree also appeared outside the lodge in Vegas when Ike the Spike attacked Dougie. There's also the squeaky foot that speaks to Jerry Horne in the woods. It sounded like a female version of the arm/tree.