[Dovecot] mbox folders on-disc layout

I'd like to change the on-disk layout for my mboxes from being ~/mail/foo/bar to ~/mail/foo.bar so that I can have folders containing both messages and subfolders, without having subfolders beginning with . and then having to do all the other fiddling with locations of index files etc. that goes along with LAYOUT=maildir++, and also leaving the filesystem layout looking sensible so my users see their mailboxes instead of the index and control files.

Is this possible or do I need to patch something?

(CentOS 6, dovecot 2.0.9)

Cheers,

John.