So I read on wikipedia that Jay-Z and Kanye West are credited on "Watch the Throne" as "The Throne", like Eminem and the other guy (I can't remember his name off the top of my head, something like Royce da 5" 9') are "Bad Meets Evil".
I know wikipedia isn't a reliable source, but it got me thinking how much I would like Rihanna to do a collaborative album/EP with someone... although I have no idea who the other person would be. The only person who comes to mind is Nicki Minaj as they get along great and have collaborated before.
Rihanna might even be able to do this with a male artist, Drake could possibly work as the chemistry between them is beyond amazing and I think they could do great things with an album like this.
Jay-Z and Kanye themselves might even be good to do this with. And the only other person I can think of right now is Katy Perry. That album, although it might not be "out there" and "pushing the envelope", it would definitely be entertaining as a side project for both Rih and Katy.
Just some thoughts running through my mind...