do you think following new functional requirment is interesting?

categorize visitors into 3 groups:
1. visitor no account in the user database
2. user register in user database
3. power user user with more authorization
Then, for each question in the database, there is an additional flag:
authorized user group
if it's set to visitor, then everybody can read it;
if it's set to user, only user and power user can read it;
if it's set to power user, only power user can read it;
a visitor can become a user after registration;
an user can become power user if he/she:
pass a certain period of time or
post a certain amount of questions or
answer a certain amount of questions.
i think this feature maybe helpful to some commercial consulting websites.
best regards