I don't know if he's the right type of fighter for Steward. He seems to like guys that use their jab a lot. Also, Steward is too widespread. He'll train Gamboa for a fight then leave afterwords to commentate on HBO and train other fighters.
Also , he's not like how he used to be when he would train fighters from the very beginning. At this point of his life, he seems more interested in training guys that are already well established (Klitschko, Taylor are examples).