Stealth-based puzzles are one way to implement a Thie- I mean Treasure Hunter job concept, but I think there's more to it than that. There's a section of Final Fantasy 6 where you have to navigate South Figaro under Imperial rule through disguises and information gathering skills. Even the idea of being able to pickpocket townspeople opens up some interesting options, à la Octopath Traveler. Who knows, maybe it could be makings of a new DoL gathering job.

If we're going to infiltrate Garlemald next expansion, with Thancred in tow no less, I don't see a better testing ground. We did have segments this expansion where we got to play as other characters, like Y'shtola.