In hindsight, when considering the absurd variety of different Garlean technologies Sicinius had access to, if Gabranth and Lyon opted to seize those from him they could feasibly build a new IVth legion by simply creating an army of autonomous magitek and super-powered clone soldiers provided they had the requisite manpower.
It did feel a little underwhelming that the Garlean empire conveniently collapsed right after they had started dabble in new technology that would've made them a horrific threat to the Eorzean Alliance, so I'm kind of hoping it ends up resurfacing in significant capacity, whether in the MSQ or sidequests.
