[gavmor]

It seems like you found a good strategy.

I might have tried earnest curiosity. "And what results would you expect from that?" or "Let's say we do this, and get such-and-such result?" or "What kind of result would diminish your confidence in this approach?"

Or, better yet, invite them to pair on the implementation! (Organizational agility permitting.)

I wonder, also, why were none of these "dead ends" accessibly documented? If so many people can offer suggestions, shouldn't they be able to see the results of prior experiments? Maybe in the form of closed tickets, at the very least.