As long as you don't ship your decision without review, and you're willing to change your mind if it's wrong, what's the problem? Like OP, I often find that people are reluctant to discuss anything that's ambiguous, until someone has made an attempt at implementing it, and presents it to them. Then, suddenly, every ambiguous choice that was decided wrongly (in someone's eye, anyway) in that attempt comes out of the wood work. It's an extraordinarily good way to spark discussions people don't want to have.
"Write one to throw away" is the greatest advice I've heard for our field. You will rarely fully explore the problem space by just talking about it ahead of time.
