The Charlotte pic is from a poster so it might be just fanservice. The Momoka thing is most definitely a plot point. Anyways from /u/
In this week radio they reveal that the production for this show were ahead by few months. They finished recording all of the episode since May this year.
In the free talk corner they talked about the time when they recorded the show. The VAs that voiced the soldiers in Mirei's flashback and Mamori's father would excuse themselves from recording booth when they dont have lines. Iguchi said it was because most of the VAs are female and they like to get too fired up talking amongst themselves. Also she basically confirmed that there will be no male character that will appear later.
They also talked about Torino's VA, Kikuko-neesan, and how she made the atmosphere in the recording booth very warm and welcoming, just like Torino herself. Apparently Kikuko-neesan did the 17 years old joke whenever they do roll call before recording. Iguchi said the moment where they retort to the joke with the "oi-oi" was the part that pump her up for the day. Also Mamori's VA, Izawa Mikako haven't told her Mom about her role as Mamori.
In the mail corner someone asked them to practice to tell Izawa's Mom about the show. Iguchi impersonation of Izawamama were funny as heck. Izawamama is someone that is motherly and would eat snack at three in the morning. Iguchi suggest to tell Izawamama about it when she was snacking so maybe she wouldn't really pay attention to what Izawa's saying. Izawa said that's not good at all.
It was very fun. I really recommend it to people that like to hear silly stuff.
Here's the link http://hibiki-radio.jp/description/vdm
Usually someone would upload the episode to niconico after few hours. Niconico is also the only place you can hear old episode of the radio.