The invention provides apparatuses and associated methods of manufacture for fuel cell systems designed for modular application. In one embodiment, a fuel cell system is provided that has a base module assembly. The base module assembly includes a first frame member and a fuel cell stack assembly coupled to the first frame member. A first subsystem module assembly is provided that includes a second frame member and a first subsystem coupled to the second frame member. A second subsystem module assembly is provided that includes a third frame member and a second subsystem coupled to the third frame member. The first frame member is coupled to each of the second and third frame members, and the second frame member is coupled to the third frame member.