Won't happen, at least not in any meaningful form.
Baltics or Poland are existentially threatened by Russia, Spain or even Germany are not, even if Russia can do a limited damage to them. What is supposed to create "unity" in that regard? What would force Spain to contribute as much as, let's say, Finland? We can see even now, with all these US threats, not every NATO country was willing to increase its spending on military. And even more importantly, who is going to command such EU army? Commission?
Nukes are but a one thing, useful only in specific circumstances, but not sufficient. It is unrealistic to expect France using nukes if Russia attacks Lithuania, for example. Stakes are not justifying such escalation.
European countries lack conventional means: UAV, artillery, missiles. And soldiers.
There is no need for anything more, nor are the institutions really designed for a single president / general to direct everyone in a conflict. Putting in place all the capabilities to work together in a conflict should be done however.
What? I'm pretty sure he said that.
Yeah, here it is: 'Army of Europe' needed to challenge Russia, says Zelensky