Kalran: Tales of the four nations/Mecha bay

With their infertility caused by the fallout. The human began to focus on mecha design, once only a minor research and limited to elites, to protect what little humans left in the event they need to support their droid army.

Due to limited pilots and frames the commander will be limited to one mecha bay. And with how much material it takes to built a single suit it will take a few before before a new mech can be made. But any pilot who escaped death and returned to the bay will shorten the build time and cost.