Feature:
The ability to create baubles that can be defined as:

• Ring
• Amulet
• Belt
• Head
• Body
• Charm
  As well as the ability to trigger a command or a potion effect that turns off when removed. Rendering the baubles on body doesn't need to be added just the ability to make them.

I really want this as well.

I arrived here because I was googling for this exact feature. I'm not sure if 1.12 is still being given new features, but I would be very interested in this ability as well. :)

While 1.12 is indeed feature complete, the reason for this never being completed, was a realization after it's creation, that it shouldn't be done in contenttweaker.