In Spain, we already deal with both Iberian and standard gauges—trains like the Talgo models can change gauges with minimal delay. It's not seamless, but it works reasonably well. Spain also has the world's second largest high speed train network.
What the EU could really benefit from is greater support for small companies and independent freelancers who are driving innovation. Unfortunately, governments (Spain included) often treat them as revenue sources, with high taxes and complex regulations, while large corporations can navigate around much of that with ease.