"Usurp authority" is an unfortunate selection for authentein. It has only the weakest support in contemporary literature. A much more likely translation is seduce. It fits both the cultural context and the textual context. In a culture where women were typically not taught the Scriptures, Paul's words were allowing more participation than the norm, not less. Further, he put a restriction only on "a woman", not "women".
1 Corinthians 11 specifically permits women to speak. If you are claiming that Paul reverses his earlier statement in chapter 14, you need to make sense of it. Also, why does he say, "What? Came the word of God out from you? Or came it unto you only?" Why does he say these particular words in this particular place in his letter? You cannot simply draw a few words out from their context and claim they are a complete truth in themselves, when in their context, they don't make sense.