On a plus side of things, they finally realize that public disorder in a newly captured city was a historical myth (or at least to the extreme they portrayed it). To add to your point, one feature that should take effect is lower economic production. The more able-bodied men you recruit then the less economic capacity you should have since the workforce is now employed in the army. They should be a threshold because initially, the recruited would not be those already working.
There are more effective and historical means to reduce expansion. Some of which they already started doing. The use of governors should increase corruption thus increasing disloyalty and rebellions among the elites. In ToB, they inexplicitly limit the number of governors which could add a great deal to the gameplay. Any attempt to reduce corruption could increase revenue but also increase dissatisfaction among the corrupt officials. In ToB and increase demand for titles could be result or rebellion by certain officials. This is paradox level of detail and CA has never shown themselves to aim for that level of sophistication. I think this may be the motivation on why CA drops features when they add new features.