You first need "ye old barber shop" and "big corp barber shop" to all agree on what this common API should be. That's the old standards proliferation problem https://xkcd.com/927/

Which is what makes it very hard to define a new common API

However, they all already agree on the standard for natural language communication (in the context of a strict, well defined domain). That's the pre-existing common API which Duplex is using