In my experience, providing data with a clear and concise reason why a particular approach would be best has worked well. If that doesn't work and the situation progresses as you described, my course of action would be to have your suggested approach documented from the start and socialized in a public forum and then when leadership directs your initial approach, use your document as a guiding document. Whatever you do, though, do NOT gloat or pull a "I told you so" 🙂. As you gain clout in the organization, other individuals will begin to put more weight on your suggestions. Hope that helps!