Through effective cooperation and coordinance, the five reasons that have been given against the formation of a European army can be resolved.
While yes different interests and goals will arise between EU nations, such an army would not adhere to them. The creation of a council of individuals that are voted from each country would alleviate in part this problem. Just as the speaker of the House of Commons in the British parliament must stay non-partisan, so should those elected individuals and vote with the benefit of Europe in mind and not their respective countries. Still, this is not a bulletproof belief. Members may still vote in the benefit of their country. A voting system of a 51% majority and the inability to veto a decision would allow for this army to be deployed faster and would remove issues like the veto of Russia in the United Nations General Assembly Resolution 68/262 about the annexation of Crimea.
When it comes to technical difficulties and the cost, these problems can be resolved relatively easily. Collectively the EU nations spend 227 billion Euros on their defense for 2018 according to the European Commission. If we combine the European defense fund (which has proposed a budget of 13 billion for 2021-2027), the transfer of a small percentage of national defense budgets to the budget of the army, and the adoption of the weapon systems of one or two countries (Germany’s or France’s which are the most technologically advanced) the result would be a well funded modern European army. This cooperation between nations would save between 25 billion and 100 billion Euros every year. Of course, soldiers from all the countries would need to be trained to use these systems and besides the economic fund, countries would need to provide the manpower for this army.
Suggesting that European countries are unable to reach a consensus on topics because of their differences is absurd. There are hundreds of articles, laws, and regulations that European nations agree are needed and that are beneficial to their respective countries. If bodies like NATO that include non-European members (USA, Canada, Turkey) can effectively communicate and manage its responsibility, it would be far easier for a European army to do this as all countries share this common European identity.
While it is true that the nature of threats has changed for the EU, the old one still loom above our heads. It was not soft power that kept Europe safe but the military might of NATO. Russia still has her eyes set on Europe and with the threats stated before by the US towards NATO, An EU army would maintain the hard power of Europe. When it comes to new threats like cyber warfare, a united European army that consists of the brightest Europeans on cyber warfare would be able to provide security for all the countries of the European Union by transferring the collective knowledge to them.