"I will consider anything you can source and generally approve anything you can convince me you can do the paperwork for without my help."
Thus far, general 3.5/PF stuff hasn't gotten called out. Spheres is on the table, and a couple dragon mag stuff. I wouldn't expect non-D&D stuff to be approved (like...idk...a rancor from Star Wars Saga Edition?), but I guess I can't rule it out.
EDIT:
And I guess it's a little bit cheating, but homebrew is maybe on the table too. I know some people have been talking about oslacamo's stuff. I'm trying to steer clear of that, though.