Basically when you type /afk, a chat message would appear saying "PlayerName is now AFK", and a 3D AFK emote would spawn on your head, but it wouldn't disappear.
When you type /afk again, it'll say "PlayerName is no longer AFK", along with the 3D AFK emote disappearing.
Edit: If 3D Emotes aren't a thing, a hat would be good enough too.
RTB Prefs for the repeating message would be neat. Like customizing the color of the chat message, and changing the looping time. Thank you and have a good day.