someday though, when technology catches up, arms would be good.It's something we will probably start seeing in 3-5 years.
A trick that the Index, Quest, Rift S, Vive could do is track the arms when they are in view of one of the cameras. Otherwise they probably wouldn't be in the field of view.
It's probably doable right now, I'd be flabbergasted if finger tracking was easier and that's largely functional right now. But for whatever reason body tracking like that hasn't been implemented yet.