IMHO we should ship things like scripts, external modules, drivers, etc with the server itself, leaving the least amount of logic in the Docker image.
What you are proposing is the opposite: introducing a templating engine that adds a level of indirection to the Docker image (the Dockerfile is generated) plus
it grabs jars, modules, scripts, xmls, etc from potentially external sources and does several patches to the server at Docker image creation time.
WRT the docker hub, I think it could be used with Concreate by using hooks, I did a quick experiment of a Dockerhub automated build having a dynamically generating a Dockerfile in [1], but I guess
the biggest question is if the added overall complexity is worth it. I'm leaning towards a -1, but would like to hear more opinions :)