Hi.
I think that the script should have a user registration form that admin will be able to customize: add, edit, delete, move fields around and require fields; including, form that user will edit info in his/her account.
I also feel that admin should be able to set free for life, free for “X” amount of time and lifetime/monthly, yearly, anually, etc paid membership subscriptions.
I also feel that admin should choose to use a recaptcha for the login and registration forms.