Yeah, everything you've said makes good sense. At the end of the day RSS is just a decent protocol for these purposes, even if more modern alternatives exist. But I think these modern alternatives are better for your purposes.
I had looked into JSON Feed or WebSub as a layer on feeds. I'm not sure it's possible but the federated thingies like ActivityPub might also give the same result, especially since Ghost supports it natively in the dashboard.
