I found a way, dont know it's exactly the same as your looking for but all the auto email creation stuff works and everything BUT if you rebuild the mail config for whatever reason you must do this again
this file also demonstrates me putting email in /home to follow the quota requirements change as your build needs this
tested on xfs system only
edit the main dovecot file
nano /etc/dovecot/dovecot.conf
and make sure
mail_location = maildir:/home/%u/%d/%n
save and exit
now the wierd part
edit this one
nano /etc/dovecot/dovecot-mysql.conf
and change all the /var/vmail links to the path you need mine is posted bellow
# following should all be on one line.
password_query = SELECT username as user, password, concat('/home/%d/', maildir) as userdb_home, concat('maildir:/home/%d/', maildir) as userdb_mail, 101 as userdb_uid, 12 as userdb_gid FROM mailbox WHERE username = '%u' AND active = '1'
# following should all be on one line
user_query = SELECT concat('/home/%d/', maildir) as home, concat('maildir:/home/%d/', maildir) as mail, 101 AS uid, 12 AS gid, CONCAT('*:messages=0:bytes=', quota) as quota_rule FROM mailbox WHERE username = '%u' AND active = '1'
iterate_query = SELECT username AS user FROM mailbox
I hope this helps it did work for me make sure to restart the dovecot service, and also move the email if needed it will not copy it