The problem with a Modelfile vs. Dockerfile is it is not clear what the primitives should be yet.
It would be like making a Dockerfile for installing OS level packages when it is best to delegate to commands to apt (etc.). Docker works at the file/os call level.
Any reason to not just use Docker as-is for model layering?
There are cloud GPU services that’ll take a docker container and run it too.
It means no project as Docker exists :-) but might be useful especially for the backwards and forwards compatibility.
You can extend Docker by having a nice tool written in Python say to do the common stuff.