It would have been somewhat impossible to create a left-wing progressive system in ancient Rome, given the technological and cultural limitations of that era.
Caesar tried to utilise the Proletarii to create a more stable system, simple because the Roman oligarchy was not only terribly oppressive, but also terribly unstable.
Nero was more of the ultimate utopian. He tried to wipe out the aristocracy physically, establish a pharaonic system, create a sort of utopian paradise out of the city of Rome and replace Roman imperialism with some kind of idealistic dream about a world culture unified in the pursuit of beauty and the arts.
The failure of Caesar is a testimony to the limitation of semi-egalitarianising social programmes in the conditions of the ancient world. While modern developing nations have more advanced technology, a lot of their technological base is resembling that of ancient Rome, in the fact that substinence agriculture and slum life is still an inherent characteristic of their societies.
The only two developing nations (not superpowers) which could have successful programmes of that kind are India and Brazil, given their size. As for the rest of the world, the change has to start either in the United States, Canada (because of its sheer size and low population density, Canada would actually be an ideal host for a progressive social transformation), Europe, Russia, China or Japan.
I think the conditions in western societies are a bit different. The institutions are too strong to mount a populist frontal charge into the heart of the system. Instead, a popular movement has to centre around a charismatic - preferably female - figure. Moreover, if we are going to mount anything today, it isn't enough with unions, but all kinds of political and non-political social movements need to be persuaded on the train, while focus should lie on an overtly emotional campaign with only a few slogans. The leadership must appear as less radical than they are, and utilise their first period in power to strengthen the organisation of their own supporters and build up alternative media channels.
The leader also needs to be somewhat young and have a good appearance. She doesn't need to actually decide anything. The only purpose of leaders should really be to be more popular than their parties in order to attract extra votes.