You’re looking at solutions for a different problem here (restricting notes or media so they’re only served to a group). We already have the base mechanisms to solve this in both Nostr and Blossom (auth & encryption). On the end-user side, Nielson is currently working on Communikeys. And a large proportion of Nostr devs are working on NIP-29, Signal-like MLS groups, or other alternatives. I’m confident that one or more of these efforts will succeed.
The underlying ask here isn’t “don’t show my media to random folks.” On the contrary, people want to post publicly. They want kind 1, and they want it to be seen. But at the same time, they also want more control over how notes and media propagate.
I know, that’s a contradictory position from the start. But it’s the position of some users who see Blossom mirroring as the villain. And, for better or worse, that’s where “solutions” like NIP-70 and what I’m discussing here come from. The goal is to let users “restrict” (or at least signal their intent to restrict) mirroring, not access.