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.

These mech not only contain powerful weaponry but also a reliable ejection system to save its pilots in the event of destruction. But pilot stocks are limited since it's complexity means that it takes roughly a million years before a pilot learns the basic of walking, which the Humans genetic memories, allowing them to retain all the skill and knowledge of their ancestors, shortens it to a month at most. And being Human in the battle they count as officer units, and therefore all of them can gain veterancy.

Due to limited pilots and frames the commander will be limited to one mecha bay per base. And with how much material it takes to built a single suit it will take a few minutes 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.