Coring as the process of people in a region adjusting to being ruled by a new set of overlords over time and ultimately giving them loyalty and legitimacy is certainly important historically and reflected in games for earlier periods, but with the increasing virulence of nationalism and ethnic identity politics since the 19th century simple old-fashioned coring no longer suffices in Europe, although there is always the possibility of a more fundamental change by changing how the people identify themselves (e.g., through adherence to a unifying transnational ideology, such as international socialism and its Soviet sponsor).
Or there is the direct approach of simply resettling populations to change permanently the character of a region, something more common in our period though bringing in loyal population to secure a region dates back to antiquity. Paradox policy stands against representing the unpleasantries involved with some WW2 demographic changes.
The autonomy system with trade-offs and concessions by master and subject and various local interest groups in different combinations and in different aspects of economics, government, and military participation seems to offer the potential to be a solid vehicle to represent the range of possible arrangements ranging from iron control to virtual independence. I think it is very promising and can be much more satisfying, but will doubtless take extensive development, testing and revisions to adjustments to fit into what is already a very complicated game.