Actually, I agree that would be a good way if it were possible.
It would be very beneficial for the proponents of free trade with, say, Red China, to show exactly all of the job gains and job losses in various areas here in the U.S. due to that trade, and to show that indeed there is a strong economic benefit to such trade with a totalitarian state.
That would indeed be a first-rate way to argue their case, but as far as I know, it has not been attempted.
But try and do a story about some factory being opened, and you'll likely lose your job for failing to consider the "human interest" angle.
The proof is in the numbers. Do you expect every individual case where companies have benefit from free trade to be listed somewhere for you to scrutinize? They are actually, you just have to look. It's called profit margins.