Michael, Michael, Michael... You are not as smart as you think you are.
depends what he plans. if he gets a coup through during the attack on earth, and then sues for terms, then he would win theoretically. he simply points to the camp and says "look! he was mistreating us as well. we're not the bad guys, he is! lets all live happily ever after together". the attack on earth, of course, will wipe out the most loyal elements of Yah-weh, and Michael is obviously planning a coup somewhere along the lines, but its a matter of timing to how well it will go.
he has to time it so that he will not have much opposition from loyalists, but also from the HEA.
he also has to time it so that he would have support for the coup from both the angels and HEA.
overall, his plan is actually pretty good in my eyes. it simply is to save the angels as a race, with him in charge when the dust settles. i think that the aim of him becoming leader has been his for a few centuries now, but the idea of being the savior has to be new. actually, if he asks for help from the HEA in overthrowing Yah-weh, he could score a few points.
in fact, his plan seems to be a bit like what the german's did after WW2; they blamed everything on Hitler where they could. the point is that Hitler himself didnt actually do much at all. his leadership style was to give vague aims in rambling speeches, and then people below him worked towards those aims. yet everyone
knows that Hitler ordered the extermination of the jews, despite there being no written evidence that he actually did. actually, thinking about it, this seems to be the plan of the demons in Hell as well, since they are blaming everything on Satan, while no doubt conveniently ignoring that they themselves were doing it just as much.
of course, in both of these cases, the leadership structure most definitely not survive intact. but then, thats because they actually succeeded in invading. if Michael can take command before an outright invasion, then surrender or sue for peace, on the grounds that it was Yah-weh who did it all, he just might scrape through. better than being executed for war crimes in the other cases. if he doesnt get command, so what? with his club, and drug ring, he will be one of the major powers of the new power structure in any case. unless it is an occupation force, in which he would be able to run a resistance group and be popular with the angels when he wins.
remember, Michael understands humans to an extent, so he would know all about Vietnam, and the tactics that could win in a war with less than advanced technology.
in fact, thinking about it, the only way he could actually lose would be for the humans to kill him. if he doesnt end up in charge, and the humans occupy Heaven, then he simply slips away, and leads a resistance group against them. the most heavily armed resistance group at that, since he is the one who has most likely got stockpiles of modern weapons hidden away somewhere in the city. the humans institute an angel run government? he would shout puppet government and lead the resistance group again.
all he has to do is avoid the humans long enough to slip away, and then he is set. its practically all one big Xanatos Gambit for him. if he survives Pantheocide, and doesnt end up in charge, as i suspect, i expect him to become the main villain against the humans. and since he can simply portal out (based on what we have seen from Uriel) when things get too hot, then it will be pretty hard to catch him. if they set up a portal detection system in heaven? then there is plenty of open space in hell where no one lives, so logically, there is plenty in heaven as well. if not, then hell would do, or even earth. it doesnt take much time to portal. he has the ultimate way of fighting a guerilla war there. portal in, lob a grenade into the surprised crowd, then portal out. BANG. dead crowd.
actually, that goes both ways, as the army/police could do the same. but a simple open the portal, lob a grenade, close portal, would be securities worst nightmare. but, the security could track the portal, and do the same. as soon as you have lobbed the bomb, you have to get out of that location through another portal, or else the security would be attacking you. it would be a fight all about speed.
and now i have rambled on quite enough i think.