The EU now contains sufficient seeds of its own destruction to ensure solutions to the problems posed by an EU Army, the Euro, and the Schengen Agreement. We wisely stayed outside the last two, we should just as wisely reject the first. As to the EU, the strains within it of countries that share nothing in common, other that they share a border (enforced or not) or a Continent, means that we should wisely get out of that as well.
The EU is never going to resume the form of simply being the Trading Block that we voted for by Referendum. The irony is that it turned from that towards political union ostensibly in order to ensure Peace. The outbreak of civil disturbance in many of its cities recently gives the lie to that. The Peace that it has enjoyed since the end of WWII was no thanks to the EU, despite it receiving the Nobel Peace Prize for that supposed achievement, but by NATO. That is the EU Army that we have always been stalwart supporters of, and should continue to do so.