I'm not so sure if it's unsustainable to build around him, even if he doesn't stick around for long.Conte is a great manager in the right head space. Problem is he will meltdown in the 2-3 season at a club, that isn’t a sustainable manager to build around despite his talent. He is basically a guy to grab an elite team of players by the balls, win a title then quit and fuck off.
Juventus rebuild their team around him and were able to continue their success even after he left. Same with Inter, they overhauled the entire squad when he was there and even after he left they only finished 2 points off first and made it to the CL final the season after that (Juve also made it to a CL final a couple seasons after he left).
Building a team with him in charge isn't really that bad, even if he isn't committed in the long term.