Thanks for sharing your idea. I have to discuss the macro thing with my colleagues, but right now I'm not sure we are able to do that in some easy way without creating some complete scripting and macro project.
But based on your description I think that instead of the macro we should be able to use these "in-entity" templates to achieve what you need. Such template would merge with the existing entity and maybe we would be able to proceed also associations (I'm not sure now).
So the template should contain some fields, some orm properties, some gedmo settings, etc. Also, such a template could contain also associations between "this" entity and another hard-coded ones, like you mentioned.
I have to discuss this with a colleague and we have to think about it. It's not a few-hours project but I believe it's not so complex.