Integration of satellite networks into 5G is considered a crucial endeavour to fully satisfy the challenging 5G connectivity requirements. In the frame of the SaT5G (Satellite and Terrestrial Network for 5G) project, advanced and innovative architecture concepts are discussed in this paper aiming at fostering satellite seamless integration within 5G networks and therefore, enabling high-value attractive solutions for satellite and terrestrial stakeholders. These options need to be further analysed and confronted to technical and economical requirements in order to propose a framework for integrated network design.