Forbid use of any password from an included list of the most easily guessable
There are none. If the plugin is active, then it is banning all of its known weak passwords.
If they try to log in with one of these weak passwords, then they will not succeed, and they will be told to use the 'Lost Password' procedure to obtain a new password.
The 3546 listed in the "common passwords list" as obtained from http://www.openwall.com/passwords/wordlists/ on 16th November 2012.
Please either send a patch, or make a donation on my donation page, and I will be glad to help. Otherwise, this plugin does all I wanted it to do and I've not got time to develop it further without some compensation.
Glad to hear that! You are looking for WordShell, http://wordshell.net.