3 locks for the topic

There was an idea. Why not add a 3rd lock for the topics?
I see it like this:

3 locks - the topic is visible only to the author and friends from the first circle (suggested by Reboot)
2 locks - the topic is visible only to blog subscribers
1 lock - the topic is visible on the main one only to blog subscribers, while everyone has the opportunity to read the topic, and it is indexed by search engines

This is just such a thought. Criticize.

UPD: And for what you lower karma? Explain yourself, please.