One other suggestion here. If the issue is that amplee, django-atompub
or flatatompub lack the ability to layer in non-atom markup you might
want to look at adding this functionality to your favorite among them,
and seeing if the changes could be rolled back into the project.
I realize this is kind of an obvious thing to say. I know I sometimes
overlook it as an option. It is a real challenge sometimes to dig into
someone else's codebase...but it's a rewarding and connecting exercise