I would test them by suggesting some shiny objects and see if they go after them. i.e. "Yes, Bob, we should do what you're suggesting but we should also do X,

I would test them by suggesting some shiny objects and see if they go after them. i.e. "Yes, Bob, we should do what you're suggesting but we should also do X, Y and Z." If they don't say "No" or something to the effect of: "Those are good suggestions but I think we really need to focus on getting a prototype out the door, some real customer feedback, etc. Then we can revisit these great suggestions and see if they are still in alignment with the product." Cheers