Wait... additional elements are a force requirement for you? Playing colonial in EU4 was unable before Conquest of Paradise? Legacy of Rome does add lot more content for Rome, just as the Sons of Abraham did for religions and the Old Gods for relative with pagan powers but in the end you can choose even with the DLCs bought whether you want to activate them for your CK2 sessions. What happens if one has no interest in having the Legacy of Rome activated? They could either not buy it or if they had it turn it off in the start off screen. Really these options are options; it was a project from upwards. These are akin expansions, adding to the game but players can choose not to adopt them. Big CK2 DLCs or expansions tend to go beyond that. Any rate for the upcoming expansion we are still going to need more information before evaluation can be more fuller.