I am currently facing this problem and would appreciate any help ...
As for setting password policies such as (default length of password, password lock after set no. of login attempts, disabling null password, etc..)
we need to make changes in /etc/pam.d/login or /etc/pam.d/system-auth files.

but these changes are set globally ....

What if i want to make it customize for specific users????
like i want to make these changes only for specific users while other system users remain unaffected.???