What would a reference implementation control plane look like?

Let's spark some discussion here so we can get the communities thoughts.

What would a reference implementation control plane look like? What are some common features/functionality people would like to see supported here?

### Things to Keep In Mind
Just some things to keep in mind:
- Let's design this in a way it's not REQUIRED to use, but there for people who need it
- Focus on common functionality that is repeated throughout the industry (service discovery on k8s, health checking, circuit breaking, etc...)
- It's okay to assert some opinion, but lets make this as generalized as possible so consumers inherit the benefits of the project without tying themselves to existing products

### Resources
Matt Klein's [blog post](https://mattklein123.dev/2020/03/15/2020-03-14-on-the-state-of-envoy-proxy-control-planes/) is a great read for those who haven't seen it.