It's been done before.
2002 - Phil Collins solo performance, Destiny's Child solo performance, Marc Anthony solo performance.
2003 - Sting solo performance, Mary J Blige solo performance with Eve, Mary J Blige again solo with Sting.
2005 - Chris Botti solo trumpet performance, Seal during Sexy Crystal Princesses, Ricky Martin solo performance.
2007 - will.i.am during Blade Runner, Heidi & Seal solo performance
, Spice Girls
lip synch solo performance, Seal during Deck the Halls.
and of course, 2011. Kanye West during Super Angels, Kanye & Jay Z solo performance, Maroon 5 during Angels Aquatic, Nikki Minaj during Pink.