Quick question though: is the only reason for using Docker containers with LaTeX file compilation for providing isolation between documents? Isn't there a performance hit versus running file compilation directly on worker machines, perhaps with some sort of folder-based isolation (workers will only compile files in folders that the user has permissions to)?
Isolation is definitely one of the main benefits for us. Compared to e.g. a chroot, docker also lets us disable networking and restrict memory etc. for the process in the container. It's another important layer of security.
Another benefit is that the Dockerfile also makes it a lot easier to manage installation of all the LaTeX packages, fonts and various scientific software that we have installed.
The overheads seem to be very low --- less than 100ms extra startup and tear down time, and no significant difference in runtime speed.