There is a way to accomplish this, but it depends on additional work landing in the Kubernetes charms from the ~Kubernetes charmer team.
While you can reasonably hook it into an AWS ELB - Juju charms strive to be as DC agnostic as possible so its easily portable between data centers and clouds. A 'one size fits most' if you will.
What I see being required, is attaching the kube-proxy service to a load balancer service (Such as nginx) and using a template generator service like confd, or consul-template, to register/render the reverse proxy / load balancer configs for the services.
At present the Kubernetes bundle only has an internally functioning network, and the networking model is undergoing some permutations. If you'd like to participate in this planning + dev cycle, the recommended location to participate is the juju mailing list: juju@lists.ubuntu.com