Very strange framework provided. How you supposed to measure success of the product if you don't even know 1) who are you users 2) what problems you would solve 3) how you solve them over solution - so there is no object of measurements yet at this stage. So metrics should be after solution provided. It only might make sense to define NS metric(-s) if we talking about existing product, but anyway to measure success of new solution will required additional metrics. Same with the Product Vision. You don't even know problem landscape to envision the way you would approach of solve it.