Firebase hosting emulator should be able to rewrite to cloud run service on localhost

Firebase hosting emulator rewrites work like a charm with firebase functions since we have functions emulator. However, rewrites to a cloud run service work only if service is deployed to the cloud. Now, since cloud run is super awesome and flexible, testing it locally is a matter of running docker image locally (with docker, docker-compose or even Kubernetes Minikube). This approach is much more flexible and a better choice than firebase functions for me.

My use case is server-side rendering. I want to be able to test locally which requests trigger rewrite to server-side rendering instance deployed to cloud run. That's possible if I use the firebase function.

Is there any way to make rewrites config work with generic URL and to be controlled with environment variable? For example, I would like to be able to configure rewrite to http://localhost:5555 when running firebase hosting emulator, and https://mycloudrunserviceurl.com when in production (or staging). This way it wouldn't matter where server-side rendering instance is deployed (Cloud Run, Firebase function, GKE, AppEngine).