What if Brutus had won?

I have been watching the HBO series "Rome," and enjoying most of it, although the storyline has become derailed by the subplot of organized crime and despite some historic errors. (For example, during the real assassination of Caesar, young Octavius was not present in the capital and his mother fled to him rather than to Anthony.) This week, the central event in the series was the defeat of Brutus by Anthony and Octavius at Philippi, but what, I am left wondering, would have happened if Brutus and the other defenders of the Roman republic had won? Could they have actually restored the republic?
The problem is, ever since the destruction of Carthage a hundred years before Philippi, Rome has inherited the entire western Mediterranean and has become a true empire. In the olden days, when Rome's power did not extend beyond Italy, Rome was a nation/state of yeoman farmers who were attached to local strongmen or to the heads of their clans, whom the yeoman elected to the Senate, and the Senate in turn elected two Consuls a year, one for war and one for peace. An empire requires an all-powerful, full time central government to administer its vast new territories and to raise funds for the hundreds of thousands of men under arms and for all the public works and roadways it must build. The old familiar, extended family and clan relationships will no longer do. Futhermore, the empire has overthrown the old economic system. No longer is food grown on small farms nor are the humble utensils of home and farm any longer made by the local blacksmith. Housewives no longer weave clothing for their families. Enormous slave plantations in Egypt and North Africa grow many tons of food and do so at a lower cost than the small Italian farms ever could. Metals come from Spain (and later from Britain) and woven and metal goods are created by slave workers in Gaul and Syria. Everything has become outsourced, so to speak. The yeoman farmers have nothing to do and have become lumpen proles in the empire's crowded cities, while the rich have become so rich they can buy the loyalty of millions and can build their own armies. Lastly, the empire has become full up with people who are no longer Roman. These new people have different religions, different customs, different expectations of what a government is. Crammed into the same cities as the now rootless Roman commoners, these new people are defining the new empire and are no longer moved by Roman traditions and loyalties. "The Tigres has been emptied into the Tibur," lamented Juvenal, and Rome was indeed changed. Octavius--with the assistance of Virgil and Livy and the other intellectuals in the empire's pay--will eventually give these new citizens a new patriotic myth, namely that the empire itself is sacred (and soon the emperor will also be named a god), and the new citizens will cling that myth rather than tales of old Roman virtue or to the Lares, the old gods of the Roman household.
Thus, what can Brutus do, even if he does win? Perhaps he could form a triumverate with some other powerful men, as Caesar did with Crassus and Pompey or as Anthony did with Octavius and Lepidus. That would not have lasted and could only have ended in more civil war. Or he could have become emperor himself. To go back to the old republic, the empire would have had to have been abandoned; the very rich would have become merely rich once more, and the rootless proles would have to have become hardworking farmers and citizen soldiers again. Every generation of Romans would have to face a foreign challenge, just as their ancestors had, and they were no more to that task than they were up to once again living a simple life, far from the corruption of the crime-ridden cities and the bread and circus they were being given by their ambitious leaders.