I did that only once and it was long ago. But don't you have to show the merchandise when you arrive at the destination? Do they give you the money back directly at the counter or do you get it back only after you showed the merchandise at the destination? I always thought that in order to get your TVA/VAT from one place back you had to have proof that you did declare the import in the other place (if it is over the limit of free stuff you can take).

I do know for a fact that the counter is before you go through security. Everyone can go there and the bathroom are common area, too.

It seems to be way too easy to do this as suggested by the OP. Also, why 17%? Isn't the TVA in France 20.1%? If you pay cash it is possible to get 10% of discount for a Rolex they have in stock. So that would be 30% total. Very nice savings. OTOH, buying the watch in Switzerland might result in even better savings.