After one of the endings, the librarian is going to get a promotion
Despite his little dialogue, he comes off as a sympathetic and friendly character. He dislikes how the Emperor has locked away knowledge of parts of Lachiem's history, to the point of risking for his well-being by allowing Lunais to access it. If you are equipped with some Viletian robes and hat you can get in the past, he will be very happy to trade them, further showing his genuine interest in history, and will call Lunais "friend" from then on. It's likely that after becoming Empress of Lachiem, Lunais will remember the librarian and give him an important position in her new instituions, as she needs open-minded people like him for her project of making Lachiem better.After two of the endings, Neliste will come to know the truth and remember Lunais
After defeating the Sandman, Lunais ascends to godhood at the price of erasing her mortal existence completely, never having existed even for Neliste who, if you completed all quests, had become her lover. However, in both variations of this ending, we can see Neliste hearing some sound and apparently going to check the source, and nothing else is seen of her. It feels like a Sequel Hook: for some reason (like the appearance of some other malicious entity) Neliste may be contacted by Meyef, made aware of their connection by becoming the only one with memories of Lunais' existence, and become the heroine of a potential sequel. However, given some similarities between this ending and the one of the original Madoka Magica series, we cannot rule out the possibility of Neliste pulling an Homura and becoming the villain, obsessed with "fixing" the timeline to get her beloved Lunais back. While Meyef wouldn't have done it out of malice, his role would be still somewhat similar to Kyubey in having instigated the whole situation.The child of Selen seen in the same ending will have a role too
Even if her name is not revealed, that little girl is quite obviously a "new" Lunais, maybe born in her place to "fix" the complete absence of the original from the new timeline, and she'll be even more similar to her as she grows up. When a new menace will surface, Lunais or Meyef will make the girl aware of their connection; Lunais may even merge with her to walk again between mortals. In case the above "evil Neliste wreaking havoc on the timeline" scenario happens, the girl will be instrumental in fighting her.Emperor Vol Terrilis was going to eradicate "deviant" sexualities
A lot of characters in the game, including the heroine, are revealed to be in the LGBTQ+ spectrum and/or engage in relationships with more than one person at a time. This would lead to the conclusion that, in the past, such range of sexualities was widely tolerated if not outright accepted in Vilete (and consequently in Lachiem, since it was formed by exiled Viletians); after all, the relationship and eventual marriage of Philia and Aelana is treated as something perfectly normal. Such utopian element, however, contrasts starkly with the dystopian society we know Vol Terrilis was building (at one point even the word "fascist" is thrown in to describe him), with many people who could be labeled "undesirables" and sent to Lachiem even for the weakest of reasons. It's likely that it wasn't among Terrilis's priorities to persecute homosexuality and such at first, also because it would have meant striking some high-ranking people while his own power wasn't still fully secured, but he changed his mind after what happened with Aelana, an high-ranking advisor who fell in love with the self-proclaimed enemy queen Philia. It was mostly out of spite against Philia, whom he probably even killed personally after her capture, if that bloodstained letter to Aelana is of any indication. In this light, the presence of so many non-straight people among the Viletian military stranded on Lachiem makes more sense: Terrilis prioritized people he'd label as "deviants" to be sent there, so that there would more chances for them to be killed, and weaken the possibly strongest opposition to the idea of purges based solely on sexual orientation.