I think you’re wildly misunderstanding how Chat AI works.
It doesn’t create characters with motivations, write plots arcs, set up twists, etc. What it does is sample huge volumes of written text, and use that to try to predict what you’re expecting it to respond with. That’s really the only innovation, and it’s infamously chaotic and unreliable.
A huge part of what makes the Hitman ambient dialog enjoyable is the creative characters like Silvio, and also the world building conversations like the guy on the phone in the service corridor of the gold gilded tower complaining how he’s expected to work a triple shift with no overtime because “it’s part of your job.”
Dialog often gets held to a lot of scrutiny - people complaining about, for example, that soldiers in Morocco said “Semper Fi” even though they’d clearly never been marines (unlike say the freelance soldiers from previous levels who’d used it).
It just wouldn’t be fun to see a guy on a phone, sneak up to hear what he’s saying and have it a world salad about his salary as a ratio to the value of a floral display in an area he has no access to or no connection to. Worse it’d be easy for the AI to think its giving you a critical clue, such as the location of the target, but have it direct you to something that doesn’t exist as described.
AI creations regularly have major issues understanding how humans operate, and what humans expect. Say if you tried to make the AI invent different mysteries for Dartmoor, you’d almost certainly run into issues where “clues” are incomprehensible to a human because the AI generated a story that relies entirely on game mechanics and samples of dialog writing.
All of the necessary guidance for a playable level would have to be created by a human, and then playtested by humans to make sure it’s actually workable… and then still never be able to replicate the very human elements that make it feel like a real mystery rather than an arbitrary logic puzzle.
Developers are already capable of putting that kind of procedural generation (everything from the Jindosh Lock in Dishonored 2 to level designs in Roguelikes) and randomness into games, and in Hitman deliberately choose to avoid it because the appeal is finding all the ways you can tinker with the clockwork palace.
Chat AI is basically a fancy toy for showing off machine learning - but it is in no way ever going to replace a real human writer, who has real human experiences and interacts with fellow humans, for making a game to be played by humans.
Also the things are notoriously easy to manipulate and hence almost invariably start going on record spouting Nazi propaganda as a result of said manipulation by people interacting with… agendas.