Creating blueprint assets/hierarchies with Python

Actually that is the case already. Virtually everything that is exposed to Blueprint is also exposed to Python. The only real limitation is that Python is intended (at least for now) to be exclusively for editor scripting, not for runtime. So it’s great for things like preparing assets in the UE4 editor, setting up a pipeline that connects UE4 to other external tools, laying out a level programmatically, etc. Were you hoping to be able to use it as a runtime scripting language?