I have suggested a similar feature before and met with little enthusiasm:
http://www.postgresql.org/message-id/D960CB61B694CF459DCFB4B0128514C2F3442B@exadv11.host.magwien.gv.at
I still think it would be a nice feature and would make pg_service.conf
more useful than it is now.
Yours,
Laurenz Albe