Feature request: Let users silently add to list via RSS

If ActivityPub will not allow for a user to add another user to a private list without following them first, would it be possible to subscribe client-side to a user's built-in RSS feed in-app instead? I'm assuming this would require adding RSS client abilities inside the app, but just for Fediverse users.

I don't know if RSS could import the same details of that post as ActivityPub, but since RSS sends no data back to User B, it might be preferable to use RSS for adding a user to a private list without following them.

The mockup shows how one can tap the RSS icon (maybe a different one?) to automatically pull up a "remotely add/remove user" menu with one's private lists. I imagine that the user's posts, even appearing client-side, can show up with an indicator that this is a remote subscription. Just like remotely subscribing to local timelines of instances, this would be client-side only and stored on device data.

Start by reviewing the existing private-list and RSS-related app flows, then compare them with the attached mockup and the ActivityPub limitation described here. Define how a client-side remote subscription would be represented, how posts would appear, and how users would add or remove accounts from private lists before implementation.