Proposal: Kubernetes Build Plugin

We propose that a build plugin and corresponding framework be added to kubernetes to facilitate: 

1. Leveraging Kubernetes' scheduling, resource allocation, and garbage collection in order to provide docker image build capabilities to users
2. Third party systems wishing to use OTS Kubernetes as a build-farm
3. Organizations using a third-party CI server to orchestrate docker image builds as part of their devops SOPs
Why would there be two build controllers?  As I understand this, there would be a single build controller responsible for controlling all builds.  Am I mis-reading?