That could work nicely, yes.

We use teams but slack is common enough.

It’s really a social issue more than a technical one. How to get people to stop playing, “guess which platform I sent you an urgent message on, which nobody else you work with uses to contact you, ever?”

Threading and history I think are necessary for the email thread set.

Yes, I agree. Email got ruined by external users - scams, spam, and marketing. Chat is nice for companies because everybody inside is trusted.

The irony is not lost on me that Booklet is almost rebuilding email, but for internal-only usage. I think about this a lot.