That's already the default behavior. You don't need to do anything special for that to work, it's what ATProto is designed for. Everything is always operating in a shared space by design.
When people "post", their posts go to their PDS's, which means that every AppView ingests data generated by every other AppView by default. There is no way to tell who's using which AppView — in fact, you can log into any AppView and your profile will be there with all your posts.
When people "post", their posts go to their PDS's, which means that every AppView ingests data generated by every other AppView by default. There is no way to tell who's using which AppView — in fact, you can log into any AppView and your profile will be there with all your posts.