I've been working on adding content generator support in Koji 1.x.
This isn't quite a clean an implementation as we'd like, but we are
currently limited by the 1.x data model.
I've been keeping the work on a branch in my personal github clone, but
I expect to merge it in to the master branch soon.
https://github.com/mikem23/koji-playground/tree/cgen
If you haven't already, you can read more about content generators here:
https://fedoraproject.org/wiki/Koji/ContentGenerators