Imo that would leave Italy and Spain and their respective union members in the dust competing against the US, China and India.
But maybe that's worth it, or maybe the Brexit will turn out great like pg said due to them not having stringent EU-type regulations on things like AI and banking (though if you're a founder leaving the EU i don't see why you'd go to the UK over the US or Canada).
Italy and Spain are heavily based on tourism and snobbery (e.g. high fashion). They ain't competing against US/China/India. And that's OK. But they need different economical policies than, for example, Germany.
