But "dropping trade restrictions, import taxes and need for touristic visas" automatically leads to production shifting towards the countries with the loosest regulation and the lowest wages. So, you need at least a supranational regulation body that tries to make regulations uniform across the zone.
But then, you need a supranational body of elected officials to jointly control that regulation body, by passing legislation.
But then, you need an executive body that sets the agenda of the legislative body. And some judiciary mechanisms to handle transgressions to the laws and regulations coming from all these organs.
And then... you basically end up with something pretty similar to the EU as we know it.
(I'm not saying the EU is perfect, mind you. Just that they didn't create such a complex collection of institutions just "for the lulz")
But then, you need a supranational body of elected officials to jointly control that regulation body, by passing legislation.
But then, you need an executive body that sets the agenda of the legislative body. And some judiciary mechanisms to handle transgressions to the laws and regulations coming from all these organs.
And then... you basically end up with something pretty similar to the EU as we know it.
(I'm not saying the EU is perfect, mind you. Just that they didn't create such a complex collection of institutions just "for the lulz")