There’s two paths forward with a TV series based on Source Code.
One is to do a police procedural where everything that happened to Colter Stevens (Gyllenhaal) in the movie has no bearing on the show. Simply introduce some nearly dead federal agents who work for Project Source Code who are transported into the bodies of civilians killed in devastating events. The agents do quick police work and stop the perpetrators from committing future atrocities. It’s like Quantum Leap or, more closely, the time-traveling procedural Seven Days – which also saw government operatives traveling back in time to prevent disasters.