As a someone that plays with a relatively tall/large avatar, my chatbox tends to get hidden in my head even at eye level, and almost completely obscured when someone is looking up at me from below. It can also get occluded by particularly tall hair, hats, ears, etc. even in normally sized avatars.
It's really frustrating to have to crouch all the way down sometimes so people can read my chatbox properly. Having others use the "chatbox in front" option is a poor solution because it then gets obscured when i'm sitting/laying down or in a short/wide avatar.
Having the option for the chatbox to render on top of your avatar would be a blessing. (To clarify, by "on top/over," I mean the chatbox itself is still below the nameplate but taking priority and being rendered in front of the avatar on-screen on parts where it would normally be behind the avatar.)
This combined with the existing chatbox opacity slider--in my and many who i've spoken to's opinions--is way more elegant than implementing a bunch of different positions and placement sliders people constantly have to fiddle with to make text easily legible for everyone's avatar.
Thanks, and I hope this is taken into consideration!