He beat a Superman who was holding back. He could never just beat Superman even with prep. He's far too slow to even do anything to Superman.
But lets focus at the topic at hand. What is he going to do to beat the other team? Blossom has the best speed feats in the battle, Goku will have to deal with her. Dexter has better feats than Batman in one week of prep for Dexter he can do some crazy shit. Much faster than anything Batman can do. If he can give a Monkey enough powers to take on characters at Goku level, there's no reason why he wouldn't do it to him self. Or hell get his monkey to fight Batman then help Blossom kill Goku.