The hard part is the early game. Once you re-establish the Roman Empire, it's just a matter of time. Don't be shy about using the Varangian Guard (mercenaries) and the Brotherhood (holy order) as soon as you get access to them. They're incredibly cheap. My play-style is very aggressive about bulking up my dynasty. Wherever I can, I set up someone from my dynasty to be the ducal viceroy. Also, a handy trick with the Byzantines is that you have a greater flexibility in choosing your heir. Default is your child born first after you become emperor (in the purple). However, there is an honorary title in which you can designate a previously born child as the heir. So breed your potential heirs aggressively before they become emperor and then after, and you have some flexibility there. All in all, the Byzantines are the best equipped to master the new mechanics given they start with ducal viceroys enabled, etc. The old play-through guides are still useful for basic strategy.

Nice job. This achievement still eludes me. Any tips for the current state of the game? A lot of the guides are outdated etc.