External Chaincode Pod on Kubernetes in Hyperledger Fabric v1.4
As you point out, Fabric v2.0 introduced external builders which are specifically targeted to allow operators to choose how their chaincodes are built and executed. With external builders it's certainly possible to trigger creation of a separate pod to launch the chaincode in.
Unfortunately, in Fabric v1.4.x there is a strong dependency on Docker. You could potentially launch your docker daemon in a separate privileged pod, and securely authenticate to it via TLS, and launch your chaincodes there. You can see the docker daemon connection configuration in the sample core.yaml.
As a warning, I'm unaware of any users which are deploying peers connecting to a remote docker daemon. I don't see any reason it should not work, but it's also not a well tested path. As external builders are available in more recent versions of Fabric, I don't expect a large amount of community support for novel docker configurations.