With the action now unfolding in the chronological and geographical center of WWII, the Nazis come onscreen (they scarcely appeared in the first three episodes) and replace the Kanto army as the primary villains. Lt. Fujishima, Shinkai's aide, has been used throughout the series to humanize the Kanto army. She serves reluctantly and loves her homeland, but despises the Nazis and, in fact, has been quite literally taken advantage of by Lingelle in particular. In contrast, Lingelle and the Nazis, portrayed as fellow travelers with the aliens and perhaps practitioners of black magic besides, quite naturally fit the role of inhuman, unadulterated evil.
Struggles between good and evil are a dime a dozen. Introducing new enemies and complicating the roles of old ones expands the plot into a struggle between good (Kishin Corps), evil (Nazis), misguided nationalism (Fujishima) and the hostile unknown (aliens). This more complicated struggle suits the thematic concerns of "Geo-Armor," which also grows more explicitly entangled with history.
In episode three Eva Braun and Bill Saguro voiced two sides of a debate about the ethics of science, with Taishi speaking for Maria in absentia. In "Panzer Knight" we see Maria Braun making music and chatting with Albert Einstein who historically represented the humanist perspective that Taishi had assigned to Maria. Depicting them together concretely connects the examination of technological ethics in "Geo-Armor" to its historical analog.
Einstein raises several new issues when he reveals that he has provided the Americans with the recipe for a super-bomb and when he speaks about the injustice of, "Men sacrificing themselves for nations when nations ought to be serving the interests of mankind."
Jack also speaks personally about this injustice when he says, "The war is being fought by adults and we're the ones paying the price." Meanwhile Eva fears that Einstein's bomb will, "Make scientists the enemies of humanity."
The potential arrival of the American bomb also complicates Kishin Corps' mission, since they must now defeat the evil enemies (within a specific time frame) without allowing their own technology to become an even greater terror. These new concerns also transform the ethical debate from a simple question of whether or not scientists are responsible for the consequences of their work into a discussion as multifaceted as the plot.
The nature of the much-sought-after control module itself is clarified in these episodes and helps build "Geo-Armor's" thematic concerns. The control modules have the ability to make anything run more efficiently and more controllably. Without them, controlling the complex mecha would be impossible for a human pilot. When Lingelle reveals the Nazi plan to mass-produce mecha, we learn that only the most mentally and physically gifted can pilot them. Such is the challenge of interfacing with a control module. In fact each pilot put into the Panzer Knight is corrupted and consumed - often before they can complete a battle. In Kishin Corps, only the select few; Bareiho, Daisaku and Kimihiko, can survive piloting the three Kishin mecha.
The propensity of Nazi pilots to hemorrhage when controlling their monstrously large and invincible super-weapon is an undeniably convenient plot device for the survival of Kishin Corps. However, it makes sense within the logic of the series' metaphors. The control modules are now defined as a piece of technology that works properly only when used by the virtuous, and thus becomes a metaphor for technology in general: Under the control of the evil and misguided they become self-destructive. Used by the heroic and virtuous (Bareiho), the control modules (meaning technology) are the best hope for defending humanity against evil and the unknown. Thus, because of the nature of the modules, the coming battle between good and evil will test the character, as well as the might, of our heroes.