> I mean double the defence budget (or triple in certain cases), double the standing army and etc.
If we would actually do defense at the EU level, we could use that money a lot more efficiently through economies of scale and 2-4% of GDP would probably be enough to defeat russia.
That would make a lot of sense. Also, if done in smart way, a significant part of the budget could be used in the service of the society during peace time.
I'd be wary of doing that, because that would mean you'd be unprepared if the peace time ends quickly.
But if we move some of those "services of the society" to the EU level, we could more efficiently run them (against, through economies of scale) and make them better at the same expanse.