I can already see it, imagine people who have their list full, removing people and replacing them would be a public passive aggressive "thing" people would do and the such drama that would follow. I'm not saying this is a bad thing, I think this would actually be a selling point of the platform, however could possibly turn into a negative part of the social culture.
What if it automatically populated the list of your "close friends" by some algorithm that ranks your overall interaction with them. So you can't arbitrarily add or remove the friends. You could "game" it but only by actually interacting with the person. If they include sentiment analysis on the interactions, then you couldn't "game" it by spamming or being a cyber bully either. You'd actually have to be friendly towards that person.
If I want to person A as a close friend, and they're not active on the platform, that should be allowed. Maximizing interactions isn't the goal, or else we wouldn't limit the feed in the first place
I think it can built so the "Feed" is restricted to "Close Friends". You can still go checkout the other friend's profiles individually. I'd also like it to be set to filter out news articles and other crap like what photos they liked ...etc.