We'd do it in Django.
Just kidding. I don't know, that's a pretty hypothetical question. We've heard nice stories about people who split up their frontend and backend into two projects, one completely Angular/Grunt, one completely Rails, where the Rails serves solely as a RESTful API and even user sign in and access checking is done through a remote service. It still sounds like a cool concept, but I'd want to have time to play around with it as a smaller experiment before really investing on a design like that. It would be a big shift in thinking, and again I don't know if it would make our lives easier or harder in the long run.