This is all very helpful, and it's great to see different perspectives.

I can assure you that for the next version there will be something along these lines.

One of the thoughts we had: Let users add their followers to the named/virtual groups which can be configured or changed anytime. Something like 'trusted', 'my previous company', 'friends' etc..

And while creating a notification: You have options 'All my followers', 'Selected followers' and a new option 'selected group(s) -> and you select one or more group'