If I'm not mistaken, he specifically could not do that before because Upgrade's technological nature could not perfectly integrate with Ben's organic nature. I suppose it is possible that this may not be the case with the improved new Omnitrix, which would also mean that he would not have Ben's voice.
when "upgrading" technology he could use the tech to build other things, like when he turned the Rustbucket into a robot similar to the Upgrade Suit.