newIdentity

I don't really see a problem with that. Also it shouldn't vibrate if you're already in the chat. So that really isn't a problem since you usually see that the other person is typing and usually wait for them to send the message as long as they aren't taking too long.

What's the disadvantage? I really only see advantages.

So here's an example:

you: hey

you: are you free right now?

other: nah. Sorry

other: but I shold have time around 17:00.

you: Ok. Call me when you're done. It's kinda important

other: Ok

The first message introduces a conversation followed by a follow up. As soon as you send the first message it's easier to send the second one too since you already introduced the conversation.

The other person then answers with a short answer where they don't really have to think about what they write and how they write it. You instantly get an answer.