> I suspect if a Service Mesh is ultimately shown to have broad value, one will make it's way into the K8S core
I'm not so sure. I suspect it'll follow the same roadmap as Gateway API, which it already kind of is with the Service Mesh Interface (https://smi-spec.io/)
Indeed, all major Service Meshes solution for Kubernetes implements (at least some part) the SMI specification.
There is a group composed of these players working actively on making such spec a standard.
Understanding these few CRDs give great insights on what do expect from a Service mesh and how thinks are typically articulated.
To me, it's a fairly big decision to layer something that's complex in it's own right on top of something else that's also complex.