Sure, that's orchestration, though. The problem with GHA is the sheer amount of expressive power that it has. If you need to do dynamic stuff then that should be in a "pre-workflow" step, written however/in whatever you please, that emits the actual workflow.
Why shouldn't the python script be the discrete workflow step? It could be mounted on some file system which has checked out the git at a particular commit with a particular tag, then runs whatever tasks are required to validate or deploy the project
