Heh, I'm also missing those two skills in my most recent playthrough of the DLC. Also DEF UP. Also I really should look at ATK and DEF UP in the code as I still have no idea what they actually do (the literal Japanese text is like "attack/def goes up easier... I have not been able to confirm through gameplay what this actually affects). I don't think those missing skills are actually broken, but are likely just obnoxious to hit the RNG for. Preparation, Formation, and Extend are all part of the Kasumi war games random event chain, so it's really up to luck that you get those. In my last playthrough I didn't even get Preparation until after day 150 (I checked some of my saves to confirm), so yeah... But, quickly peeking at the code, it looks like that event chain all share the same trigger and it just iterates through them until you've done them all, at which point it'll do a generic Kasumi power event instead. Unless the variable that tracks that progress somehow gets set to the wrong value (it's a local variable and it looks fine to me) it should be functioning properly. As an aside, I find it quite funny how Inusuku doesn't disable random event calls even after very significant plot points. Destroy the Gate, Town is saved, here cumsyor semen.
Thanks for the vote of confidence in my writing, heh. Naturally I'm trying to match my concept for how the characters would speak and act as best I can, and I feel weeby af doing it as I'm constantly thinking about if lines would be reasonable to say in Japanese, but in the end it can't help but be my interpretation. Art will also be a hangup, I kind of want to extend some scenes just with more variety but mostly re-used (or maybe... modified?) assets as the writing and code are not nearly such a barrier for me. Then there's balancing the pace of content, as adding primarily weekend events would make the week a slog, though I do have some very silly ideas for extended weekday content as well (it needs art, but maybe it's doable).
Ultimately though I am very concerned with things that have potential to worsen the experience, or things people would feel they want to actively avoid. Of course anything I add will be togglable, but it's like... it personally makes me uneasy. Beyond gameplay mods, stuff that expands on character interactions and relationships feels weird, like inserting a doujin into the actual game. I dunno, there's stuff I'd like to see with these characters but at some point I really should just be making my own damn game, ya know?