WoJ is that the Blackstaff chooses his own successor...
Can you find the cite for that, please? I've seen it before, several times, so I believe you.
Thing is, the citation that
I know about says something else:
Would you tell us how a person gets choosen to be The Blackstaff of the White Council?
Heh. He picks up the Blackstaff with full knowledge of what he’s in for if he does. If you can find someone crazy enough to do that, and reliable enough to be trusted with it, he gets the job.
-- https://wordof.jim-butcher.com/index.php/word-of-jim-woj-compilation/woj-on-harrys-mortal-allies/
I don't think the Gatekeeper, Warden, or Blackstaff are offices of the Council, I think they are offices that when held are usually held by members of the Council. The Merlin and the Sr Council are the only offices of the Council. (well Peabody's and other administrative offices exist... as does the Commander of the wardens (little w))
I don't think we have WoJ on this, but I agree with you.
"Blackstaff" is an unofficial title, an acknowledgement of how-things-are. Ditto "Gatekeeper."
I'm not even sure they're aware of "whoever is linked to Demonreach" actually being a "Warden," to be honest. I think it would
Freak Them the F'k Out to learn that there is a
Warden (with a cap-W), and that Harry Dresden is it: there being a
Warden rather implies that such a person is in charge of their (small-w) wardens (since both the Well/prison and the White Council itself are the OG Merlin's work...) .