Rejecting weak passwords

Dear hackers,

I have been thinking about ways to have PostgreSQL reject
weak passwords.

I think the standard recommendation is "use PAM and LDAP",
but that requires the user to change the password outside
of PostgreSQL. And who would want to setup and maintain an
LDAP server just for this?

Since everybody has different ideas what is a good password,
there should be some way to configure that. I've looked at
how Oracle does it, and they simply let you write a
stored procedure that throws an exception if it doesn't
like the password.
Since users are on cluster level and functions live in
databases, that won't work in PostgreSQL.

I have come up with an idea or two and like to hear your
opinion.

1) One could have a set of GUCs like min_password_length,
min_password_nonchars and similar that everybody
could configure. This is not extremely flexible though.
2) Another idea would be a GUC that contains a regular
expression that a password may *not* match.
Perhaps that's too limiting too.
3) I have also considered a GUC that points to a loadable
module that performs the password check if set.

Are there better ways?

Yours,
Laurenz Albe