I think I'd have to disagree. I can't see how a universal bishop can ever be a legitimate development. If the Pope is universal bishop then surely no other bishop is really bishop at all. I can absolutely see a single bishop as head bishop within (not over) the Church as a possibly acceptable development (which is I guess what we would say the primacy of Rome should be) but he still needs to be subject to the Church and not the other way around.
Sorry, I don't men universal in that way. But universal that he is somewhat a "Patriarch of Patriarchs". Definitely not in the current authority of the Pope of Rome, but similar to what a Patriarch is today, but over the whole Church.