Under one aspect, a system generates dynamic call models within an IMS network, allowing different user entities (UEs) to have different service experiences. The IMS network includes application servers (ASs) and a serving call state control function (S-CSCF) that receives and then forwards UE service requests. The system includes storage media storing a service tree, which defines potential call models that map potential UE service requests onto ASs. At least two potential call models map a specified potential UE service request onto different ASs that can provide different service experiences. The system includes control logic for providing session control, which receives UE service requests from the S-CSCF, receives the service tree from the storage media, generates a call model for each UE based on potential call models defined by the service tree and on the requested service, and invokes a specified AS based on the generated call model.