Join Date: Mar 2008
Location: Rochester, Medway, Kent.
Looking at it that way I suppose a lot would depend on the manner of his waking up.
If he just happens to roll over, fart, have a scratch and ask for a cup of coffee then the transition could be a little easier.
If, on the other hand, it's the whole rebirth scenario then I can see problems.
It would be a nightmare just proving he is the Emperor, dealing with the masses screaming "Heretic!" and "He turned me into a newt!" would be even tougher to deal with.
As for the High Lords and the rest of Terra's hierarchy, they would follow the Emperor unless they have ulterior motives, how many of them really have the interests of the Imperium at heart and how many are in it for the power the position brings?
Some would side with the Emperor, of course they would, but there would be plenty who wouldn't and with the current state of affairs the last thing the Imperium or the Emperor would want would be another civil war.
If the Emperor woke up I think he would have to start the process all over again, including working in the background until humanity was ready again.