It would be good to offer a possibility of displaying stanza numbers at the beginning of every line, perhaps also with a different appearance than when they are first set.
Workarounds using (short)InstrumentName have some shortcomings, see the threads from
http://lists.gnu.org/archive/html/lilypond-user/2016-06/msg00469.html and
http://lists.gnu.org/archive/html/lilypond-user/2016-07/msg00005.html.