Model-based development has become state of the art in software engineering. A number of tools, like Matlab/ Simulink or SCADE, are available for the automatic generation of application code on basis of models. Unfortunately, system aspects like process management, communication or fault-tolerance mechanisms are not covered by these tools. One main reason is the non-existence of appropriate models with an explicit semantic to allow the automatic code generation. In addition, there is a great need to have the possibility to extend both the model and the code generation abilities to allow a high coverage of the used platforms, since such code is platform dependent. In this paper, we will present an approach applying meta code generators using template-based code generation to achieve this extensibility and will discuss the properties of models required for the use in model-based development of system aspects for safety-critical real-time systems.