Keri Hilson is good, but she has been sucky lately. And people do not know here name nearly as well.
MJB is nice for an old school feel, so she would not fit AOTL. This song is futuristic and Epic. Her voice is not as anthemic as Rihanna's. We are not in the 90s either.
Rihanna's voice was MADE for the radio, and anything she touches is golden. On hip-hop hooks she is masterful (i.e Run This Town, Live Your Life, Love the Way You Lie) She is God of the radio right now and has been for a while. He needs a hit. She will help with that.