I've had to deal with this exact situation in the past, and I went through the same rationale. My experience: you wind up constantly iterating, hoping for smal

I've had to deal with this exact situation in the past, and I went through the same rationale. My experience: you wind up constantly iterating, hoping for small "wins" - where the expectations of your PM matches something you've produced. But these are far and few in-between. You need world-class people who've lead projects to save and push things forward. The success of the project depends on whether you have someone on the team who's willing to stand up and push their own vision, and whether your PM is willing to budge. You WILL have to do mockups to some fidelity, just realize that your PM won't appreciate the work and the complexity that goes into it.