All users can enter as one user "puser" without superuser priviledges: how?

I seek a simplistic access,

1. superuser "postgres" gets access when his system-name is "postgres",
   but not otherwise [some security sought].
   This can be done in pg_hba.conf with either
      local all  peer sameuser
      local all trust   #but anyone then gets "postges" access.

2. One other user, say "puser", gets access whatever his system-name.
   The above
      local all peer sameuser
   disallows an arbitrary username entering as  "psql template1 -U puser".
   One can use
      host all 127.0.0.1 255.0.0.0 ident jimsmap
   then have pg_ident.conf  with 1000 user entries like
      jimsmap    jameson  puser
   However, I seek a simpler method for numerous users,
   each of whom will be granted access as user "puser".
   ANY IDEAS?




--
Jameson C. Burt, NJ9L   Fairfax, Virginia, USA
jameson@coost.com       http://www.coost.com
(202) 690-0380 (work)