I'll try to explain this as best I can:
Have the script run through a set of characters randomly that will stop at a pre-determined password strength? Let's say you create a new account, and set the username, use this url, counter, etc, then click on a button and the script will go through characters (that the user has specified) until it reaches or exceeds a password strength the user has set.
Say I put:
0123456789abcdef
and the script will randomize this:
0a3190cedff212d
or whatever until it reaches the pw strength specified.
Which brings me to my other idea:
Enter whatever characters you want and click a button that will randomize those characters automatically. But, unlike my idea above, this feature should only use a character once:
0123456789abcdef
randomized:
0af21de34b59c678
So, instead of having the standard 0-9a-z or whatever, this should mix things up a bit.