Since CA has already mentioned that it is impossible to mod in features like Family Tree in Rome II, the only alternative people have is to have these features being included in the new DLCs.
I think while having a more focused campaign is nice, there is really a need for DLCs that adds a new level of immersion for the players. I think there is a fairly significant portion of the fan base that will welcome DLCs that adds more role-playing features as well as features that makes the game more challenging.
I think one of the major selling point for the previous Total War games is that you are able to role-play a dynasty and control the actions of "characters" rather than the nation state as a whole. As much as people care about the long History of Legio X in their campaign, they also cared about who is in command of the legion, and whether the Imperial dynasty will collapse because of their last heir was a lunatic.
DLCs really should reintroduce old features from Rome I, as a way to attract fans who are simply more interested in playing a game with the old features. This way, this could actually extend the shelf-life of Rome II because fans will want to play a Roman era game with the features they enjoy.