Join Date: Mar 2008
Location: Rochester, Medway, Kent.
I don't think the Big E waking up would really make much difference, in the long term at least. For a short time there would be a huge rise in Imperial morale but the Imperium would still be in the same crap position it was in before he went for a nap.
The Tyranids, Necrons and Tau are new threats that weren't around during the great crusade and the Empire is no longer in a position of control that it had in the wake of the fall of the Eldar.
The only real change he could make would be to take control away from the High Lords of Terra and the Inquisition, and I'm not sure they would go quietly.
Ultimately he would have to start the whole process again and hope that the forces of Chaos were not looking.
Pull back all the Space Marine chapters back to as close to Terra as was safe and start conquering worlds again, either with the old Imperial Truth or some new doctrine and dogma.