Hi Alex
We tried promoting this field using entries in a table (can't remember off-hand but we put an X in all of the fields)
It works fine.. as long as (as you said) your design allows for it.
After promotion we found that the roles now amalgamated the individual field values into one org level component thus losing the granularity it had at object level.
Reversing the promotion left us with the same amalgamated values but now in the separate auth objects rather than restoring the individual values.
Cheers
David