This is going to sound crazy, but my vote goes for Kweli. Hear me out. The man is an incredible emcee, you can't dispute that whether or not you like his beats. Mos Def is incredible, but the Roots have moved on beyond the Double Trouble era. Common is talented, but will not be able to hold his own with Thought when it comes to the Roots' beats and Thought's flow. Common needs a specific style or he sounds lost. Kweli, on the other hand, is incredibly versatile and is comfortable with Thought's and the Roots' style. He's an incredible lyricist who will be able to provide quality rhymes to compliment Thought. Moreover, Kweli sounds better in group situations. He always sounds more at home with other people in the song. Plus, (this is a clincher) he's lost his direction nowadays. The man's still incredibly talented and the Roots could help him get back on track. They'll give him quality beats and the work he needs to hop back on. Moreover, if it's commercial attention he's after, he's going to get that so much more on Def Jam than on Koch.

More than anyone, though, I want Malik B back.