So the disconnect here, I feel, is that you're listing entirely characters whose deals we already know. The people you listed we know the least about are Edda, who is on the council and so who we see at least some of every turn, and Gunnars, who we've had a bunch of interactions with but just keep failing at getting information out of. This seems like a rich-get-richer situation, where the only characters who get our social actions are the ones we have preexisting relationships with.
I want to social Oswald because we don't know much about him. Like, yes, I will agree with you 100% that I am certain I will find interactions with Kazador interesting in a way that I am not certain I will find interactions with Oswald interesting (except insofar as I trust Boney to write interesting stuff all the time forever), but I feel that with five social actions a turn, we can afford to spare one on the "explore" side of the "explore-exploit" strategic dichotomy. The dude has had all of two paragraphs, only one of them onscreen. I want to give him a chance to impress us.
See. I value a compact cast of characters who we value, who have substantial layers to them and interesting dynamics with the protagonist. I despise expanding the character roster for the sake of expanding it. We've got a ton of people we've interacted with and who have interesting stories I'd like to see more of that I feel trying to turn over rocks in the search of more interesting things is missing the point. It's the same premise why we don't actively try and find more projects given our AP shortage. There are more interesting characters than we'll ever be satisfied wiht.
Oswald doesn't have any inherent value, we haven't seen particular signs of depths, and their relationship dynamic is 'we interviewed him once'. You want something new, don't just latch onto Oswald- look for signs that the character has interesting depth, look at their possible relationship dynamic with Mathilde, look at characters liable to matter in narrative terms. For instance;
Hluodwica- she's the priestess of Esmerelda and leader of the Halflings, she's relevant and liable to be a character that might show up more and bounce off Mathilde. She has lots of potential interesting details between her leadership and her faith, she's interconnected with Mathilde through their romance book club and by virtue of Mathilde trying to get a prestess of Esmerelda teaching the We. Bam. I can say there's a lot more to be interested in then Oswald.
Ruprecht- he's the leader of Ulrikadrin and Grand Master. He's a character who we can expect to potentially engage meaningfully with the story and has a lot of baggage both in why he left the Empire, what he thinks of his choices leading up to here, and what living close by but outside of K8P is like. As for their relationship? They're both warriors, he thought she was investigating whether or not he needed to disappear and they both think Wolves are neat. Bam. Plenty of potential black comedy, insight into the Empire, association with humanity, and things to bond over.
Just because we can choose who we interact with and we can trust Boney doesn't mean we shouldn't put forth some due diligence in trying to find interesting potential of our own. I'd much rather we put more thought into the kinds of interactions we want to see than 'that cat was a gag in one scene! It's a sign'.
Edit: When I say that look for characters that are liable to matter I'm not saying use the Social turns to try and pursue advantage, I'm saying look for interesting characters liable to make an impact on Mathilde. To influence her story. We loved Abelheim because of how he shaped Mathilde, we followed Belebro because of how he engaged with us, Kragg has been awesome because of how he's infected and humored Mathilde, etc. Characters are at their best and most enjoyable when they have a meaningful impact on the protagonist. There's nothing wrong in looking for those impacts.