I'm sure that this would be helpful for anyone friend/VIP rank or above, so I definitely agree. Maybe not this specific command, because there are other ways to do hide that you're in the game, but this seems good enough.
Also, you said;
Then people would notice that someone is missing on the list, and that would be pretty weird. I don't have any solution that would work well other than having their name appear differently on tab and list, but that would probably be similar to /disguise in a sense.