jayvdb added a comment.
Tightly related, but orthogonal, is https://phabricator.wikimedia.org/T67196, which is allows multiple accounts to be used concurrently. The code to solve that bug will be a lot more stable if it is done after step 1 (allow config.usernames to be a list of usernames per site) above.
TASK DETAIL https://phabricator.wikimedia.org/T71283
EMAIL PREFERENCES https://phabricator.wikimedia.org/settings/panel/emailpreferences/
To: jayvdb Cc: gerritbot, XZise, jayvdb, Ricordisamoa, pywikipedia-bugs