Separate follower/friend lists with accompanying scope
This feature is intended for users that don't use alts at all.
The problem that this feature tries to solve is that you want to be publicly followable but still want to make private statuses for an inner circle. (Given my personal account, I have around 50+ follow requests of people I don't know close enough, which I don't accept because I want my follower-only statuses to stay private.)
The solution is to make a subset of the follower list which I call friend list. You can mark a follower as "friend", you'll also have another scope called "Friends-only". Now since this is a subset of followers, if the "friend" unfollows you, it basically ends the friendship and the friend-only statuses are inaccessible after that.
Let me know what you think.