If I understood correctly, Harry didn't invent a new potion, he found it one of the books that Flitwick recommended. And if you assume that Draco still has Snape's support, it won't be easy for Harry to find more powerful potions than Draco.

It also seems clear that the teachers involved think that inventing new potions is far too dangerous with Harry's current level of experience (which is basically none). That's why I don't think that more potions will be the way to Chaos' success. At least not the critical factor.