Low Earth Orbit (LEO) satellite constellations are attracting a lot of interest in research as they promise high-throughput low-latency communication all over the world. This aspect makes them perfect candidates for including them in existing vehicular networks. In this paper we motivate a holistic simulation model for hybrid LEO satellite and ground-based Vehicle-to-Everything (V2X) networks, then present its challenges, approaches to overcome them, and a proof of concept simulation.