This should be native to the protocol in place of NIP-02. NIP-51 should be NIP-02 in my mind. NIP-51 is simply "Lists". There is also kind 30000 identifiers for "Sets of lists" which can include people. As well as kind 10000 sets of lists which can include muted users.

Amethyst and Nostrudel and maybe a couple of other clients can generate a feed from these lists. While it's not optimal, it does work. I am of the opinion this can be optimized, and needs to be.

Personally I don't believe there is value in a global feed outside of niche exceptions. Sometimes there is value in peering into a well. But I don't believe there is much value once a user followed over 100 people. Even 50 follows can be overwhelming without filtering.