Setting aside the financial nightmare, I think you are basically right. Paxton is intriguing, and Segura is solid enough, but it takes a sledge hammer to our depth for relatively minimal upside. King Felix is middle relief, maybe gets a boost in the NL, but I can't imagine anybody will take him on.
Hayes needs to basically be untouchable, since he along with Keller at least give us some hopes of keeping our window of mediocrity extended indefinitely into the future. Reynolds and Newman might be depth pieces, maybe more, and I think the intuition to protect Williams is also right. Right now, we have strong depth at pitching, and in a sense, I don't see much of a reason to tinker. Kingham and Brault are fine as #6 and #7 depth guys, and Keller should be able to start forcing the issue partway into the season. "Worst" case scenario there and we can try to flip Nova at the deadline, but regardless of how that happens, Keller is basically primed to step in and take over once Nova's contract is up.
Williams isn't exactly the most showstopping player on paper, but it seems like a decent bet that his floor is a pretty consummate backend rotation piece. There's just no reason to give that up in what might be a lateral move. Paxton definitely has a lot of upside, but we need to focus all of our energy on offense. That's what sucks, since it seems pretty difficult to identify reasonable upgrades via trade or free agency, and most of the options seem to not move the needle enough, anyways. It's a backhanded compliment, but Huntington has truly done a great job of locking us into being a solid, .500 team.
There are definitely some things we should be trying to do this offseason, but the more I think on it as we really get underway, it seems like basically the most likely huge improvement would come because of something unexpected, like Hayes cracking in next year, or Tucker, etc. Or Archer turning into a full-fledged ace and having a nasty 1-2 combo at SP.