Constructive argument? Just disband the EU as a whole, including all laws, treaties, contracts ...
Europe would be a much better place if the EU stayed what it was, a trade union of sovereign nations without any political power over the people.
The EU was never just a trade union.
How would this have worked in practice though? How could things like trade standards been harmonised or a common currency adopted without the trade union being able to do legislation?
And once you get there, you're no longer a trade union. Or a trading block, which is probably the better word since a trade union already means something else.