external scheduler
While Docker is da hype these days, there are other virtualization options out there that may, depending on environment, be a more interesting way to create a virtual environment.
It would be useful if gitlab CI would support other ways of starting virtualized builds. Ideally, the "start a VM" bit would be done by way of a shell script or some such that a local admin can then customize, and which just returns the IP address or hostname or whatnot on which the new VM is then running; gitlab CI can then use its normal/regular SSH ways of connecting to it.