I gotta disagree. It's true that we don't really know as many of the personalities in many of the barbarian tribes, but they absolutely had the sort of character-driven conflicts that CK2 models much better than EU, as did the more established powers. Consider the role the conflict between Hamilcar's family and Hanno the Great played in the origins and progress of the Second Punic War, or the various succession wars that devastated the various Diadochi states. That's not even taking into account the various barbarian tribes, where personal relations were even more important. EU works best with relatively unified states that have established infrastructure, which sorta, kinda works for some periods of e.g. the Roman Republic, or the Diadochi, but doesn't really represent the period as a whole as well.
Now ideally, a hypothetical Rome II would be a hybrid game that took the best from both worlds (a modified version of the EUIV trade system for instance), but I would expect the final product to be closer to CK than EU in mechanics.