I don't know that happiness matters. My favorite teacher drives me insane--hardly makes me happy at all until I get through one of his damn classes and realize I learned far more than I ever thought possible. I respect him. I don't know him at all, so I can't say whether I like him or not--but he's a superb teacher, and I also trust him to know how to teach me.
Isn't that more important that ArbCom earns or has the respect of the community? Than that they make the community happy? The latter seems to be the way to set them up for no community support. If their job is defined well, and they do it well, and they're able to do it well because the requirements for doing so are not so onerous, then they will, imo, wind up with the community's support for taking upon themselves a thankless job. But happiness? How could they provide that?
Not everyone is mature enough to respect someone they don't like. The worry is not so much that people would be unhappy with ArbCom, but that that unhappiness would cause them not to respect ArbCom. Without respect, the committee is pretty much pointless.