Sure, you don't register a header unless there is paper somewhere that
describes the proper way to use it. That could always include an internet
draft in the case of a provisional registration.
We need more than documentation to use headers widely, we need good design.
And experience suggests that fields designed by individual implementors
aren't suitable for widespread use.
Indeed so, which is why a mechanism that forces at least an internet draft
(which automatically provides a forum for discussion) and that causes the
registration to lapse if the draft is not pursued to RFC status would
provide some degree of control.
I agree with the need to publically discuss and vett new fields before they
are widely implemented. I'm not sure about the idea of accepting registrations
in advance of approval, and having them lapse if not approved.
Keith