Just a thought that I had, but what if they implemented a "turn the roman empire roman" feature? it would have to be impossibly difficult to pull off, given how difficult it would have been in real life.
So, you just conquered all of the land necessary to reform the roman empire? not that great, because it isn't actually roman! Whenever you think of Rome, you think a bunch of people in togas discussing how angry Jupiter must have been that day to have sent such a great storm their way, not a bunch of Italians and Greeks arguing about some guy named Jesus (didn't we crucify him? Constantine truly was the worst emperor ever). No, you must become truly Roman and recreate Rome the way it was when the first Caesar reigned. Thus you are given an option to adopt the Roman culture and religion (hellenic? this is Rome, not Greece, get out of here). If you choose to become the most Roman (descriptor) Roman (religion) Roman (culture) ever, good luck, because living hell awaits you.
You, my friend have just decided to wear nothing but togas and speak nothing but latin, and nobody else in the entire world does either one. In fact, I think everybody would agree that doing these would be taking this whole "I'm the emperor of Rome!" thing way too far. Therefore, every single one of your vassals and courtiers now has a -50 opinion malus because "my liege is insane and wears weird clothes". Oh well, at least mercenaries don't care how crazy you are. Also, no way they want their kids raised like that, so they will always refuse whenever you offer to educate their kids. Oh, but that's not all, because all of your non-Indian neighbors are thinking "my ancestors died to rid the world of the roman menace, and now they are back? lets show them who's boss!", giving them a cultural "holy war" cb on you (the targets would be kingdoms because they already have the religious holy war for duchies) and a -200 opinion malus just to make sure they hate everything you represent in the world. Also, all of their vassals get a +200 "at war with filthy romans" opinion boost while at war with you, meaning all of your enemies are superpowered badasses whenever you are at war (whether offensive or defensive). Oh, dear, your vassals just revolted because they all suddenly hate you? here comes the entirety of the world to take all of your land. Of course, since you are the rightful emperor of the entire world, you can declare the same cultural "holy war" on them to take them out by the kingdom, but that's hardly a relief since you probably no longer exist.
All is not lost, however, since it is indeed possible to convince your vassals and courtiers to embrace the toga, but only if they have a high enough opinion of you (good luck, since basically all your vassals and courtiers are now zealous about their culture). once you have managed to convert your vassals, they will work to spread it to the peasants just like what happens with every other culture (if having Scotland being awarded Jerusalem in a crusade eventually turns the Jerusalemite peasants Scottish, than choosing to become Roman should make your peasants eventually turn Roman). Of course, since you basically just invented a religion and culture, you won't be able to summon holy men or nobles of the Roman culture or religion until you have converted a province to be properly Roman Roman (once you have either the culture or religion converted, it should be much easier to do the other, for reasons that seem obvious to me), instead summoning people of the religion and culture of your capital.
So basically, you can turn Rome into a Roman Roman Rome that would make Augustus Caesar proud, but in order to do so, you must placate your vassals who all of a sudden hate you, defeat supercharged enemies who are primed to take all of your land in one fell swoop, and wait as RNGesus Romanizes Rome. Now, all I need is for everyone to pick apart my idea, showing how stupid it is just like what happened with the first guy to suggest something like it.