Does openAI support that stuff, or is that a more general MLOps (or whatever you'd call it) list of functionality you need? The API call aspect seems like a pretty easy part that's not a barrier to switching models. It's whatever customizations for a given application that I'd expect to be more work. But re your text I quoted, I'm always wary of "one line of code" solutions that are harder to customize than it would be to just write the the thing.
all that stuff is what we needed to do to support multiple providers vs hard-coding a single one. none of it is specific to our codebase. if we were going to take on a third-party dependency, we'd need it to be serious about this kind of thing, else we have an external dependency to work around on our critical path
Edit: As an example, if the switching layer doesn't implement model negotiation and doesn't expose key model details (which vary by model provider service, and often require REST calls to introspect), we can't add model negotiation / retries / etc on top, and would have to edit the innards to enable that, which opens up all sorts of questions