I still think we should change DIOCWDINFO to write the raw label,
even if there is no raw label.  Currently DIOCWDINFO will fail
if the raw label doesn't exist.  (See disklabel(5)).

Each port can then ensure that it updates its NetBSD disklabel, and
if necessary update the "vendor"/"PROM" label (e.g, on Sun boxes).

disklabel(8) would have all "write to the actual sectors of the raw label"
support removed.
(For that matter, it should have the '-B' (bootblock) stuff removed as well.)

This all should be ok if the securelevel is enforced appropriately
by DIOCWDINFO.