I don’t think it’s currently possible, but I think it is absolutely necessary to allow for notifications of new subscribers, bits, and followers. There are plenty of ways to do it, and I have no idea why it’s not currently part of the API.
I’m not sure if this is a comment or a question, but all of these are definitely possible. It’s how overlays display new followers, subscribers, and Bits. You can use IRC for a lot of these messages. You could also use the follows API or subscriptions API. For Bits, we also have PubSub in addition to IRC.