Here is a good mod suggesions.
When users try to enter certain parts of the site (private area), the script will check to see if the user is login or not (using UBB database). If not login he will be forwarded to a page for him/her to login his/her username and password. If they have a correct username/password, they will be granted access. Otherwise they will get a denied message with information on how they can register.
What do you think can this sort of mod be done?