Presented are shock-force mitigation systems for fuel cell stacks, methods for making/using such systems, and electric-drive vehicles equipped with such systems. A fuel cell system includes multiple electrochemical fuel cells that are stacked face-to-face along a stack axis to define a fuel cell stack. A push plate abuts each longitudinal end of the fuel cell stack; these push plates translate rectilinearly along the stack axis inside a fuel cell stack housing. An end plate is located in facing spaced relation to each push plate to define a plate pair at each end of the stack. An active or passive force-modifying device is interposed between the two plates in each plate pair; these devices modify stack forces experienced by the fuel cell stack. For an active shock-force mitigation system, each force-modifying device may include a bladder system, spring, and/or linear actuator; an electronic system controller controls activation of the bladders/actuators.