I can entertain that this idea could be a solution IF done well, but what would be the path to democratic decision-making in this integrated EU? I strongly believe in people organising against the government, I think this is what can lead to change, or at least maintain the fighting spirit going.

The EU is handicapped by its very diversity on this. Imagine the situation where the EU is integrated, and the government wants to pass Chat Control 2.0, or some equally unsavoury measure. Imagine that some people or orgs manage to whip up the people of the Netherlands into protesting in the streets against it: it's extremely unlikely that Poles or Spaniards would be able to build a protest movement on top of that, if they were even aware of it, because of language and national sentiment ("it's just some people over there being angry about whatever, and mainstream media says there's nothing to see there, or that they're evil terrorists, and I don't understand their funny language enough to check").

There are some promising moves towards a EU-wide party in Mera25 for example (if I understand it correctly), but it's ultimately a party for English-speaking, basically well-off, educated, currently left-leaning, young people, which is nothing that one can build a deep movement on.